4 Documents Ganeti version |version|
13 This document serves as a more example-oriented guide to Ganeti; while
14 the administration guide shows a conceptual approach, here you will find
15 a step-by-step example to managing instances and the cluster.
17 Our simulated, example cluster will have three machines, named
18 ``node1``, ``node2``, ``node3``. Note that in real life machines will
19 usually FQDNs but here we use short names for brevity. We will use a
20 secondary network for replication data, ``192.168.2.0/24``, with nodes
21 having the last octet the same as their index. The cluster name will be
22 ``example-cluster``. All nodes have the same simulated hardware
23 configuration, two disks of 750GB, 32GB of memory and 4 CPUs.
25 On this cluster, we will create up to seven instances, named
26 ``instance1`` to ``instance7``.
32 Follow the :doc:`install` document and prepare the nodes. Then it's time
33 to initialise the cluster::
35 node1# gnt-cluster init -s 192.168.2.1 --enabled-hypervisors=xen-pvm cluster
38 The creation was fine. Let's check that one node we have is functioning
42 Node DTotal DFree MTotal MNode MFree Pinst Sinst
43 node1 1.3T 1.3T 32.0G 1.0G 30.5G 0 0
44 node1# gnt-cluster verify
45 Mon Oct 26 02:08:51 2009 * Verifying global settings
46 Mon Oct 26 02:08:51 2009 * Gathering data (1 nodes)
47 Mon Oct 26 02:08:52 2009 * Verifying node status
48 Mon Oct 26 02:08:52 2009 * Verifying instance status
49 Mon Oct 26 02:08:52 2009 * Verifying orphan volumes
50 Mon Oct 26 02:08:52 2009 * Verifying remaining instances
51 Mon Oct 26 02:08:52 2009 * Verifying N+1 Memory redundancy
52 Mon Oct 26 02:08:52 2009 * Other Notes
53 Mon Oct 26 02:08:52 2009 * Hooks Results
56 Since this proceeded correctly, let's add the other two nodes::
58 node1# gnt-node add -s 192.168.2.2 node2
60 Performing this operation is going to replace the ssh daemon keypair
61 on the target machine (node2) with the ones of the current one
62 and grant full intra-cluster ssh root access to/from it
64 The authenticity of host 'node2 (192.168.1.2)' can't be established.
65 RSA key fingerprint is 9f:…
66 Are you sure you want to continue connecting (yes/no)? yes
67 root@node2's password:
68 Mon Oct 26 02:11:54 2009 - INFO: Node will be a master candidate
69 node1# gnt-node add -s 192.168.2.3 node3
71 Performing this operation is going to replace the ssh daemon keypair
72 on the target machine (node2) with the ones of the current one
73 and grant full intra-cluster ssh root access to/from it
75 The authenticity of host 'node3 (192.168.1.3)' can't be established.
76 RSA key fingerprint is 9f:…
77 Are you sure you want to continue connecting (yes/no)? yes
78 root@node2's password:
79 Mon Oct 26 02:11:54 2009 - INFO: Node will be a master candidate
81 Checking the cluster status again::
84 Node DTotal DFree MTotal MNode MFree Pinst Sinst
85 node1 1.3T 1.3T 32.0G 1.0G 30.5G 0 0
86 node2 1.3T 1.3T 32.0G 1.0G 30.5G 0 0
87 node3 1.3T 1.3T 32.0G 1.0G 30.5G 0 0
88 node1# gnt-cluster verify
89 Mon Oct 26 02:15:14 2009 * Verifying global settings
90 Mon Oct 26 02:15:14 2009 * Gathering data (3 nodes)
91 Mon Oct 26 02:15:16 2009 * Verifying node status
92 Mon Oct 26 02:15:16 2009 * Verifying instance status
93 Mon Oct 26 02:15:16 2009 * Verifying orphan volumes
94 Mon Oct 26 02:15:16 2009 * Verifying remaining instances
95 Mon Oct 26 02:15:16 2009 * Verifying N+1 Memory redundancy
96 Mon Oct 26 02:15:16 2009 * Other Notes
97 Mon Oct 26 02:15:16 2009 * Hooks Results
100 And let's check that we have a valid OS::
110 Now that the cluster is created, it is time to check that the hardware
111 works correctly, that the hypervisor can actually create instances,
112 etc. This is done via the debootstrap tool as described in the admin
113 guide. Similar output lines are replaced with ``…`` in the below log::
115 node1# /usr/lib/ganeti/tools/burnin -o debootstrap -p instance{1..5}
116 - Testing global parameters
125 * Submitted job ID(s) 157, 158, 159, 160, 161
126 waiting for job 157 for instance1
128 waiting for job 161 for instance5
129 - Replacing disks on the same nodes
131 run replace_on_secondary
132 run replace_on_primary
135 run replace_on_secondary
136 run replace_on_primary
137 * Submitted job ID(s) 162, 163, 164, 165, 166
138 waiting for job 162 for instance1
140 - Changing the secondary node
142 run replace_new_secondary node3
144 run replace_new_secondary node1
147 run replace_new_secondary node1
148 * Submitted job ID(s) 167, 168, 169, 170, 171
149 waiting for job 167 for instance1
153 increase disk/0 by 128 MB
156 increase disk/0 by 128 MB
157 * Submitted job ID(s) 173, 174, 175, 176, 177
158 waiting for job 173 for instance1
160 - Failing over instances
164 * Submitted job ID(s) 179, 180, 181, 182, 183
165 waiting for job 179 for instance1
167 - Migrating instances
169 migration and migration cleanup
172 migration and migration cleanup
173 * Submitted job ID(s) 184, 185, 186, 187, 188
174 waiting for job 184 for instance1
176 - Exporting and re-importing instances
180 import from node3 to node1, node2
186 import from node1 to node2, node3
188 * Submitted job ID(s) 196, 197, 198, 199, 200
189 waiting for job 196 for instance1
191 - Reinstalling instances
193 reinstall without passing the OS
194 reinstall specifying the OS
197 reinstall without passing the OS
198 reinstall specifying the OS
199 * Submitted job ID(s) 203, 204, 205, 206, 207
200 waiting for job 203 for instance1
202 - Rebooting instances
204 reboot with type 'hard'
205 reboot with type 'soft'
206 reboot with type 'full'
209 reboot with type 'hard'
210 reboot with type 'soft'
211 reboot with type 'full'
212 * Submitted job ID(s) 208, 209, 210, 211, 212
213 waiting for job 208 for instance1
215 - Adding and removing disks
223 * Submitted job ID(s) 213, 214, 215, 216, 217
224 waiting for job 213 for instance1
226 - Adding and removing NICs
234 * Submitted job ID(s) 218, 219, 220, 221, 222
235 waiting for job 218 for instance1
237 - Activating/deactivating disks
239 activate disks when online
240 activate disks when offline
241 deactivate disks (when offline)
244 activate disks when online
245 activate disks when offline
246 deactivate disks (when offline)
247 * Submitted job ID(s) 223, 224, 225, 226, 227
248 waiting for job 223 for instance1
250 - Stopping and starting instances
254 * Submitted job ID(s) 230, 231, 232, 233, 234
255 waiting for job 230 for instance1
261 * Submitted job ID(s) 235, 236, 237, 238, 239
262 waiting for job 235 for instance1
266 You can see in the above what operations the burnin does. Ideally, the
267 burnin log would proceed successfully through all the steps and end
268 cleanly, without throwing errors.
276 At this point, Ganeti and the hardware seems to be functioning
277 correctly, so we'll follow up with creating the instances manually::
279 node1# gnt-instance add -t drbd -o debootstrap -s 256m -n node1:node2 instance3
280 Mon Oct 26 04:06:52 2009 - INFO: Selected nodes for instance instance1 via iallocator hail: node2, node3
281 Mon Oct 26 04:06:53 2009 * creating instance disks...
282 Mon Oct 26 04:06:57 2009 adding instance instance1 to cluster config
283 Mon Oct 26 04:06:57 2009 - INFO: Waiting for instance instance1 to sync disks.
284 Mon Oct 26 04:06:57 2009 - INFO: - device disk/0: 20.00% done, 4 estimated seconds remaining
285 Mon Oct 26 04:07:01 2009 - INFO: Instance instance1's disks are in sync.
286 Mon Oct 26 04:07:01 2009 creating os for instance instance1 on node node2
287 Mon Oct 26 04:07:01 2009 * running the instance OS create scripts...
288 Mon Oct 26 04:07:14 2009 * starting instance...
289 node1# gnt-instance add -t drbd -o debootstrap -s 256m -n node1:node2 instanc<drbd -o debootstrap -s 256m -n node1:node2 instance2
290 Mon Oct 26 04:11:37 2009 * creating instance disks...
291 Mon Oct 26 04:11:40 2009 adding instance instance2 to cluster config
292 Mon Oct 26 04:11:41 2009 - INFO: Waiting for instance instance2 to sync disks.
293 Mon Oct 26 04:11:41 2009 - INFO: - device disk/0: 35.40% done, 1 estimated seconds remaining
294 Mon Oct 26 04:11:42 2009 - INFO: - device disk/0: 58.50% done, 1 estimated seconds remaining
295 Mon Oct 26 04:11:43 2009 - INFO: - device disk/0: 86.20% done, 0 estimated seconds remaining
296 Mon Oct 26 04:11:44 2009 - INFO: - device disk/0: 92.40% done, 0 estimated seconds remaining
297 Mon Oct 26 04:11:44 2009 - INFO: - device disk/0: 97.00% done, 0 estimated seconds remaining
298 Mon Oct 26 04:11:44 2009 - INFO: Instance instance2's disks are in sync.
299 Mon Oct 26 04:11:44 2009 creating os for instance instance2 on node node1
300 Mon Oct 26 04:11:44 2009 * running the instance OS create scripts...
301 Mon Oct 26 04:11:57 2009 * starting instance...
304 The above shows one instance created via an iallocator script, and one
305 being created with manual node assignment. The other three instances
306 were also created and now it's time to check them::
308 node1# gnt-instance list
309 Instance Hypervisor OS Primary_node Status Memory
310 instance1 xen-pvm debootstrap node2 running 128M
311 instance2 xen-pvm debootstrap node1 running 128M
312 instance3 xen-pvm debootstrap node1 running 128M
313 instance4 xen-pvm debootstrap node3 running 128M
314 instance5 xen-pvm debootstrap node2 running 128M
319 Accessing an instance's console is easy::
321 node1# gnt-instance console instance2
322 [ 0.000000] Bootdata ok (command line is root=/dev/sda1 ro)
323 [ 0.000000] Linux version 2.6…
324 [ 0.000000] BIOS-provided physical RAM map:
325 [ 0.000000] Xen: 0000000000000000 - 0000000008800000 (usable)
326 [13138176.018071] Built 1 zonelists. Total pages: 34816
327 [13138176.018074] Kernel command line: root=/dev/sda1 ro
328 [13138176.018694] Initializing CPU#0
330 Checking file systems...fsck 1.41.3 (12-Oct-2008)
332 Setting kernel variables (/etc/sysctl.conf)...done.
333 Mounting local filesystems...done.
334 Activating swapfile swap...done.
335 Setting up networking....
336 Configuring network interfaces...done.
337 Setting console screen modes and fonts.
338 INIT: Entering runlevel: 2
339 Starting enhanced syslogd: rsyslogd.
340 Starting periodic command scheduler: crond.
342 Debian GNU/Linux 5.0 instance2 tty1
346 At this moment you can login to the instance and, after configuring the
347 network (and doing this on all instances), we can check their
350 node1# fping instance{1..5}
361 Removing unwanted instances is also easy::
363 node1# gnt-instance remove instance5
364 This will remove the volumes of the instance instance5 (including
365 mirrors), thus removing all the data of the instance. Continue?
370 Recovering from hardware failures
371 ---------------------------------
373 Recovering from node failure
374 ++++++++++++++++++++++++++++
376 We are now left with four instances. Assume that at this point, node3,
377 which has one primary and one secondary instance, crashes::
379 node1# gnt-node info node3
381 primary ip: 172.24.227.1
382 secondary ip: 192.168.2.3
383 master candidate: True
386 primary for instances:
388 secondary for instances:
393 At this point, the primary instance of that node (instance4) is down,
394 but the secondary instance (instance1) is not affected except it has
395 lost disk redundancy::
397 node1# fping instance{1,4}
399 instance4 is unreachable
402 If we try to check the status of instance4 via the instance info
403 command, it fails because it tries to contact node3 which is down::
405 node1# gnt-instance info instance4
406 Failure: command execution error:
407 Error checking node node3: Connection failed (113: No route to host)
410 So we need to mark node3 as being *offline*, and thus Ganeti won't talk
413 node1# gnt-node modify -O yes -f node3
414 Mon Oct 26 04:34:12 2009 - WARNING: Not enough master candidates (desired 10, new value will be 2)
415 Mon Oct 26 04:34:15 2009 - WARNING: Communication failure to node node3: Connection failed (113: No route to host)
418 - master_candidate -> auto-demotion due to offline
421 And now we can failover the instance::
423 node1# gnt-instance failover --ignore-consistency instance4
424 Failover will happen to image instance4. This requires a shutdown of
425 the instance. Continue?
427 Mon Oct 26 04:35:34 2009 * checking disk consistency between source and target
428 Failure: command execution error:
429 Disk disk/0 is degraded on target node, aborting failover.
430 node1# gnt-instance failover --ignore-consistency instance4
431 Failover will happen to image instance4. This requires a shutdown of
432 the instance. Continue?
434 Mon Oct 26 04:35:47 2009 * checking disk consistency between source and target
435 Mon Oct 26 04:35:47 2009 * shutting down instance on source node
436 Mon Oct 26 04:35:47 2009 - WARNING: Could not shutdown instance instance4 on node node3. Proceeding anyway. Please make sure node node3 is down. Error details: Node is marked offline
437 Mon Oct 26 04:35:47 2009 * deactivating the instance's disks on source node
438 Mon Oct 26 04:35:47 2009 - WARNING: Could not shutdown block device disk/0 on node node3: Node is marked offline
439 Mon Oct 26 04:35:47 2009 * activating the instance's disks on target node
440 Mon Oct 26 04:35:47 2009 - WARNING: Could not prepare block device disk/0 on node node3 (is_primary=False, pass=1): Node is marked offline
441 Mon Oct 26 04:35:48 2009 * starting the instance on the target node
444 Note in our first attempt, Ganeti refused to do the failover since it
445 wasn't sure what is the status of the instance's disks. We pass the
446 ``--ignore-consistency`` flag and then we can failover::
448 node1# gnt-instance list
449 Instance Hypervisor OS Primary_node Status Memory
450 instance1 xen-pvm debootstrap node2 running 128M
451 instance2 xen-pvm debootstrap node1 running 128M
452 instance3 xen-pvm debootstrap node1 running 128M
453 instance4 xen-pvm debootstrap node1 running 128M
456 But at this point, both instance1 and instance4 are without disk
459 node1# gnt-instance info instance1
460 Instance name: instance1
461 UUID: 45173e82-d1fa-417c-8758-7d582ab7eef4
463 Creation time: 2009-10-26 04:06:57
464 Modification time: 2009-10-26 04:07:14
465 State: configured to be up, actual state is up
469 Operating system: debootstrap
470 Allocated network port: None
472 - root_path: default (/dev/sda1)
473 - kernel_args: default (ro)
474 - use_bootloader: default (False)
475 - bootloader_args: default ()
476 - bootloader_path: default ()
477 - kernel_path: default (/boot/vmlinuz-2.6-xenU)
478 - initrd_path: default ()
483 - nic/0: MAC: aa:00:00:78:da:63, IP: None, mode: bridged, link: xen-br0
485 - disk/0: drbd8, size 256M
487 nodeA: node2, minor=0
488 nodeB: node3, minor=0
490 auth key: 8e950e3cec6854b0181fbc3a6058657701f2d458
491 on primary: /dev/drbd0 (147:0) in sync, status *DEGRADED*
493 - child 0: lvm, size 256M
494 logical_id: xenvg/22459cf8-117d-4bea-a1aa-791667d07800.disk0_data
495 on primary: /dev/xenvg/22459cf8-117d-4bea-a1aa-791667d07800.disk0_data (254:0)
496 - child 1: lvm, size 128M
497 logical_id: xenvg/22459cf8-117d-4bea-a1aa-791667d07800.disk0_meta
498 on primary: /dev/xenvg/22459cf8-117d-4bea-a1aa-791667d07800.disk0_meta (254:1)
500 The output is similar for instance4. In order to recover this, we need
501 to run the node evacuate command which will change from the current
502 secondary node to a new one (in this case, we only have two working
503 nodes, so all instances will be end on nodes one and two)::
505 node1# gnt-node evacuate -I hail node3
506 Relocate instance(s) 'instance1','instance4' from node
507 node3 using iallocator hail?
509 Mon Oct 26 05:05:39 2009 - INFO: Selected new secondary for instance 'instance1': node1
510 Mon Oct 26 05:05:40 2009 - INFO: Selected new secondary for instance 'instance4': node2
511 Mon Oct 26 05:05:40 2009 Replacing disk(s) 0 for instance1
512 Mon Oct 26 05:05:40 2009 STEP 1/6 Check device existence
513 Mon Oct 26 05:05:40 2009 - INFO: Checking disk/0 on node2
514 Mon Oct 26 05:05:40 2009 - INFO: Checking volume groups
515 Mon Oct 26 05:05:40 2009 STEP 2/6 Check peer consistency
516 Mon Oct 26 05:05:40 2009 - INFO: Checking disk/0 consistency on node node2
517 Mon Oct 26 05:05:40 2009 STEP 3/6 Allocate new storage
518 Mon Oct 26 05:05:40 2009 - INFO: Adding new local storage on node1 for disk/0
519 Mon Oct 26 05:05:41 2009 STEP 4/6 Changing drbd configuration
520 Mon Oct 26 05:05:41 2009 - INFO: activating a new drbd on node1 for disk/0
521 Mon Oct 26 05:05:42 2009 - INFO: Shutting down drbd for disk/0 on old node
522 Mon Oct 26 05:05:42 2009 - WARNING: Failed to shutdown drbd for disk/0 on oldnode: Node is marked offline
523 Mon Oct 26 05:05:42 2009 Hint: Please cleanup this device manually as soon as possible
524 Mon Oct 26 05:05:42 2009 - INFO: Detaching primary drbds from the network (=> standalone)
525 Mon Oct 26 05:05:42 2009 - INFO: Updating instance configuration
526 Mon Oct 26 05:05:45 2009 - INFO: Attaching primary drbds to new secondary (standalone => connected)
527 Mon Oct 26 05:05:46 2009 STEP 5/6 Sync devices
528 Mon Oct 26 05:05:46 2009 - INFO: Waiting for instance instance1 to sync disks.
529 Mon Oct 26 05:05:46 2009 - INFO: - device disk/0: 13.90% done, 7 estimated seconds remaining
530 Mon Oct 26 05:05:53 2009 - INFO: Instance instance1's disks are in sync.
531 Mon Oct 26 05:05:53 2009 STEP 6/6 Removing old storage
532 Mon Oct 26 05:05:53 2009 - INFO: Remove logical volumes for 0
533 Mon Oct 26 05:05:53 2009 - WARNING: Can't remove old LV: Node is marked offline
534 Mon Oct 26 05:05:53 2009 Hint: remove unused LVs manually
535 Mon Oct 26 05:05:53 2009 - WARNING: Can't remove old LV: Node is marked offline
536 Mon Oct 26 05:05:53 2009 Hint: remove unused LVs manually
537 Mon Oct 26 05:05:53 2009 Replacing disk(s) 0 for instance4
538 Mon Oct 26 05:05:53 2009 STEP 1/6 Check device existence
539 Mon Oct 26 05:05:53 2009 - INFO: Checking disk/0 on node1
540 Mon Oct 26 05:05:53 2009 - INFO: Checking volume groups
541 Mon Oct 26 05:05:53 2009 STEP 2/6 Check peer consistency
542 Mon Oct 26 05:05:53 2009 - INFO: Checking disk/0 consistency on node node1
543 Mon Oct 26 05:05:54 2009 STEP 3/6 Allocate new storage
544 Mon Oct 26 05:05:54 2009 - INFO: Adding new local storage on node2 for disk/0
545 Mon Oct 26 05:05:54 2009 STEP 4/6 Changing drbd configuration
546 Mon Oct 26 05:05:54 2009 - INFO: activating a new drbd on node2 for disk/0
547 Mon Oct 26 05:05:55 2009 - INFO: Shutting down drbd for disk/0 on old node
548 Mon Oct 26 05:05:55 2009 - WARNING: Failed to shutdown drbd for disk/0 on oldnode: Node is marked offline
549 Mon Oct 26 05:05:55 2009 Hint: Please cleanup this device manually as soon as possible
550 Mon Oct 26 05:05:55 2009 - INFO: Detaching primary drbds from the network (=> standalone)
551 Mon Oct 26 05:05:55 2009 - INFO: Updating instance configuration
552 Mon Oct 26 05:05:55 2009 - INFO: Attaching primary drbds to new secondary (standalone => connected)
553 Mon Oct 26 05:05:56 2009 STEP 5/6 Sync devices
554 Mon Oct 26 05:05:56 2009 - INFO: Waiting for instance instance4 to sync disks.
555 Mon Oct 26 05:05:56 2009 - INFO: - device disk/0: 12.40% done, 8 estimated seconds remaining
556 Mon Oct 26 05:06:04 2009 - INFO: Instance instance4's disks are in sync.
557 Mon Oct 26 05:06:04 2009 STEP 6/6 Removing old storage
558 Mon Oct 26 05:06:04 2009 - INFO: Remove logical volumes for 0
559 Mon Oct 26 05:06:04 2009 - WARNING: Can't remove old LV: Node is marked offline
560 Mon Oct 26 05:06:04 2009 Hint: remove unused LVs manually
561 Mon Oct 26 05:06:04 2009 - WARNING: Can't remove old LV: Node is marked offline
562 Mon Oct 26 05:06:04 2009 Hint: remove unused LVs manually
565 And now node3 is completely free of instances and can be repaired::
568 Node DTotal DFree MTotal MNode MFree Pinst Sinst
569 node1 1.3T 1.3T 32.0G 1.0G 30.2G 3 1
570 node2 1.3T 1.3T 32.0G 1.0G 30.4G 1 3
573 Re-adding a node to the cluster
574 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
577 Let's say node3 has been repaired and is now ready to be
578 reused. Re-adding it is simple::
580 node1# gnt-node add --readd node3
581 The authenticity of host 'node3 (172.24.227.1)' can't be established.
582 RSA key fingerprint is 9f:2e:5a:2e:e0:bd:00:09:e4:5c:32:f2:27:57:7a:f4.
583 Are you sure you want to continue connecting (yes/no)? yes
584 Mon Oct 26 05:27:39 2009 - INFO: Readding a node, the offline/drained flags were reset
585 Mon Oct 26 05:27:39 2009 - INFO: Node will be a master candidate
587 And is now working again::
590 Node DTotal DFree MTotal MNode MFree Pinst Sinst
591 node1 1.3T 1.3T 32.0G 1.0G 30.2G 3 1
592 node2 1.3T 1.3T 32.0G 1.0G 30.4G 1 3
593 node3 1.3T 1.3T 32.0G 1.0G 30.4G 0 0
595 .. note:: If you have the ganeti-htools package installed, you can
596 shuffle the instances around to have a better use of the nodes.
601 A disk failure is simpler than a full node failure. First, a single disk
602 failure should not cause data-loss for any redundant instance; only the
603 performance of some instances might be reduced due to more network
606 Let take the cluster status in the above listing, and check what volumes
609 node1# gnt-node volumes -o phys,instance node2
621 You can see that all instances on node2 have logical volumes on
622 ``/dev/sdb1``. Let's simulate a disk failure on that disk::
625 node2# echo offline > /sys/block/sdb/device/state
627 /dev/sdb1: read failed after 0 of 4096 at 0: Input/output error
628 /dev/sdb1: read failed after 0 of 4096 at 750153695232: Input/output error
629 /dev/sdb1: read failed after 0 of 4096 at 0: Input/output error
630 Couldn't find device with uuid '954bJA-mNL0-7ydj-sdpW-nc2C-ZrCi-zFp91c'.
631 Couldn't find all physical volumes for volume group xenvg.
632 /dev/sdb1: read failed after 0 of 4096 at 0: Input/output error
633 /dev/sdb1: read failed after 0 of 4096 at 0: Input/output error
634 Couldn't find device with uuid '954bJA-mNL0-7ydj-sdpW-nc2C-ZrCi-zFp91c'.
635 Couldn't find all physical volumes for volume group xenvg.
636 Volume group xenvg not found
639 At this point, the node is broken and if we are to examine
640 instance2 we get (simplified output shown)::
642 node1# gnt-instance info instance2
643 Instance name: instance2
644 State: configured to be up, actual state is up
649 - disk/0: drbd8, size 256M
650 on primary: /dev/drbd0 (147:0) in sync, status ok
651 on secondary: /dev/drbd1 (147:1) in sync, status *DEGRADED* *MISSING DISK*
653 This instance has a secondary only on node2. Let's verify a primary
656 node1# gnt-instance info instance1
657 Instance name: instance1
658 State: configured to be up, actual state is up
663 - disk/0: drbd8, size 256M
664 on primary: /dev/drbd0 (147:0) in sync, status *DEGRADED* *MISSING DISK*
665 on secondary: /dev/drbd3 (147:3) in sync, status ok
666 node1# gnt-instance console instance1
668 Debian GNU/Linux 5.0 instance1 tty1
670 instance1 login: root
671 Last login: Tue Oct 27 01:24:09 UTC 2009 on tty1
672 instance1:~# date > test
674 instance1:~# cat test
675 Tue Oct 27 01:25:20 UTC 2009
676 instance1:~# dmesg|tail
677 [5439785.235448] NET: Registered protocol family 15
678 [5439785.235489] 802.1Q VLAN Support v1.8 Ben Greear <greearb@candelatech.com>
679 [5439785.235495] All bugs added by David S. Miller <davem@redhat.com>
680 [5439785.235517] XENBUS: Device with no driver: device/console/0
681 [5439785.236576] kjournald starting. Commit interval 5 seconds
682 [5439785.236588] EXT3-fs: mounted filesystem with ordered data mode.
683 [5439785.236625] VFS: Mounted root (ext3 filesystem) readonly.
684 [5439785.236663] Freeing unused kernel memory: 172k freed
685 [5439787.533779] EXT3 FS on sda1, internal journal
686 [5440655.065431] eth0: no IPv6 routers present
689 As you can see, the instance is running fine and doesn't see any disk
690 issues. It is now time to fix node2 and re-establish redundancy for the
693 .. note:: For Ganeti 2.0 we need to fix manually the volume group on
694 node2 by running ``vgreduce --removemissing xenvg``
698 node1# gnt-node repair-storage node2 lvm-vg xenvg
699 Mon Oct 26 18:14:03 2009 Repairing storage unit 'xenvg' on node2 ...
701 VG #PV #LV #SN Attr VSize VFree
702 xenvg 1 8 0 wz--n- 673.84G 673.84G
705 This has removed the 'bad' disk from the volume group, which is now left
706 with only one PV. We can now replace the disks for the involved
709 node1# for i in instance{1..4}; do gnt-instance replace-disks -a $i; done
710 Mon Oct 26 18:15:38 2009 Replacing disk(s) 0 for instance1
711 Mon Oct 26 18:15:38 2009 STEP 1/6 Check device existence
712 Mon Oct 26 18:15:38 2009 - INFO: Checking disk/0 on node1
713 Mon Oct 26 18:15:38 2009 - INFO: Checking disk/0 on node2
714 Mon Oct 26 18:15:38 2009 - INFO: Checking volume groups
715 Mon Oct 26 18:15:38 2009 STEP 2/6 Check peer consistency
716 Mon Oct 26 18:15:38 2009 - INFO: Checking disk/0 consistency on node node1
717 Mon Oct 26 18:15:39 2009 STEP 3/6 Allocate new storage
718 Mon Oct 26 18:15:39 2009 - INFO: Adding storage on node2 for disk/0
719 Mon Oct 26 18:15:39 2009 STEP 4/6 Changing drbd configuration
720 Mon Oct 26 18:15:39 2009 - INFO: Detaching disk/0 drbd from local storage
721 Mon Oct 26 18:15:40 2009 - INFO: Renaming the old LVs on the target node
722 Mon Oct 26 18:15:40 2009 - INFO: Renaming the new LVs on the target node
723 Mon Oct 26 18:15:40 2009 - INFO: Adding new mirror component on node2
724 Mon Oct 26 18:15:41 2009 STEP 5/6 Sync devices
725 Mon Oct 26 18:15:41 2009 - INFO: Waiting for instance instance1 to sync disks.
726 Mon Oct 26 18:15:41 2009 - INFO: - device disk/0: 12.40% done, 9 estimated seconds remaining
727 Mon Oct 26 18:15:50 2009 - INFO: Instance instance1's disks are in sync.
728 Mon Oct 26 18:15:50 2009 STEP 6/6 Removing old storage
729 Mon Oct 26 18:15:50 2009 - INFO: Remove logical volumes for disk/0
730 Mon Oct 26 18:15:52 2009 Replacing disk(s) 0 for instance2
731 Mon Oct 26 18:15:52 2009 STEP 1/6 Check device existence
733 Mon Oct 26 18:16:01 2009 STEP 6/6 Removing old storage
734 Mon Oct 26 18:16:01 2009 - INFO: Remove logical volumes for disk/0
735 Mon Oct 26 18:16:02 2009 Replacing disk(s) 0 for instance3
736 Mon Oct 26 18:16:02 2009 STEP 1/6 Check device existence
738 Mon Oct 26 18:16:09 2009 STEP 6/6 Removing old storage
739 Mon Oct 26 18:16:09 2009 - INFO: Remove logical volumes for disk/0
740 Mon Oct 26 18:16:10 2009 Replacing disk(s) 0 for instance4
741 Mon Oct 26 18:16:10 2009 STEP 1/6 Check device existence
743 Mon Oct 26 18:16:18 2009 STEP 6/6 Removing old storage
744 Mon Oct 26 18:16:18 2009 - INFO: Remove logical volumes for disk/0
747 As this point, all instances should be healthy again.
749 .. note:: Ganeti 2.0 doesn't have the ``-a`` option to replace-disks, so
750 for it you have to run the loop twice, once over primary instances
751 with argument ``-p`` and once secondary instances with argument
752 ``-s``, but otherwise the operations are similar::
754 node1# gnt-instance replace-disks -p instance1
756 node1# for i in instance{2..4}; do gnt-instance replace-disks -s $i; done
758 Common cluster problems
759 -----------------------
761 There are a number of small issues that might appear on a cluster that
762 can be solved easily as long as the issue is properly identified. For
763 this exercise we will consider the case of node3, which was broken
764 previously and re-added to the cluster without reinstallation. Running
765 cluster verify on the cluster reports::
767 node1# gnt-cluster verify
768 Mon Oct 26 18:30:08 2009 * Verifying global settings
769 Mon Oct 26 18:30:08 2009 * Gathering data (3 nodes)
770 Mon Oct 26 18:30:10 2009 * Verifying node status
771 Mon Oct 26 18:30:10 2009 - ERROR: node node3: unallocated drbd minor 0 is in use
772 Mon Oct 26 18:30:10 2009 - ERROR: node node3: unallocated drbd minor 1 is in use
773 Mon Oct 26 18:30:10 2009 * Verifying instance status
774 Mon Oct 26 18:30:10 2009 - ERROR: instance instance4: instance should not run on node node3
775 Mon Oct 26 18:30:10 2009 * Verifying orphan volumes
776 Mon Oct 26 18:30:10 2009 - ERROR: node node3: volume 22459cf8-117d-4bea-a1aa-791667d07800.disk0_data is unknown
777 Mon Oct 26 18:30:10 2009 - ERROR: node node3: volume 1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_data is unknown
778 Mon Oct 26 18:30:10 2009 - ERROR: node node3: volume 1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_meta is unknown
779 Mon Oct 26 18:30:10 2009 - ERROR: node node3: volume 22459cf8-117d-4bea-a1aa-791667d07800.disk0_meta is unknown
780 Mon Oct 26 18:30:10 2009 * Verifying remaining instances
781 Mon Oct 26 18:30:10 2009 * Verifying N+1 Memory redundancy
782 Mon Oct 26 18:30:10 2009 * Other Notes
783 Mon Oct 26 18:30:10 2009 * Hooks Results
789 As you can see, *instance4* has a copy running on node3, because we
790 forced the failover when node3 failed. This case is dangerous as the
791 instance will have the same IP and MAC address, wreaking havok on the
792 network environment and anyone who tries to use it.
794 Ganeti doesn't directly handle this case. It is recommended to logon to
797 node3# xm destroy instance4
799 Unallocated DRBD minors
800 +++++++++++++++++++++++
802 There are still unallocated DRBD minors on node3. Again, these are not
803 handled by Ganeti directly and need to be cleaned up via DRBD commands::
805 node3# drbdsetup /dev/drbd0 down
806 node3# drbdsetup /dev/drbd1 down
812 At this point, the only remaining problem should be the so-called
813 *orphan* volumes. This can happen also in the case of an aborted
814 disk-replace, or similar situation where Ganeti was not able to recover
815 automatically. Here you need to remove them manually via LVM commands::
817 node3# lvremove xenvg
818 Do you really want to remove active logical volume "22459cf8-117d-4bea-a1aa-791667d07800.disk0_data"? [y/n]: y
819 Logical volume "22459cf8-117d-4bea-a1aa-791667d07800.disk0_data" successfully removed
820 Do you really want to remove active logical volume "22459cf8-117d-4bea-a1aa-791667d07800.disk0_meta"? [y/n]: y
821 Logical volume "22459cf8-117d-4bea-a1aa-791667d07800.disk0_meta" successfully removed
822 Do you really want to remove active logical volume "1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_data"? [y/n]: y
823 Logical volume "1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_data" successfully removed
824 Do you really want to remove active logical volume "1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_meta"? [y/n]: y
825 Logical volume "1aaf4716-e57f-4101-a8d6-03af5da9dc50.disk0_meta" successfully removed
828 At this point cluster verify shouldn't complain anymore::
830 node1# gnt-cluster verify
831 Mon Oct 26 18:37:51 2009 * Verifying global settings
832 Mon Oct 26 18:37:51 2009 * Gathering data (3 nodes)
833 Mon Oct 26 18:37:53 2009 * Verifying node status
834 Mon Oct 26 18:37:53 2009 * Verifying instance status
835 Mon Oct 26 18:37:53 2009 * Verifying orphan volumes
836 Mon Oct 26 18:37:53 2009 * Verifying remaining instances
837 Mon Oct 26 18:37:53 2009 * Verifying N+1 Memory redundancy
838 Mon Oct 26 18:37:53 2009 * Other Notes
839 Mon Oct 26 18:37:53 2009 * Hooks Results
845 Since redundant instances in Ganeti have a primary/secondary model, it
846 is needed to leave aside on each node enough memory so that if one of
847 its peer node fails, all the secondary instances that have that node as
848 primary can be relocated. More specifically, if instance2 has node1 as
849 primary and node2 as secondary (and node1 and node2 do not have any
850 other instances in this layout), then it means that node2 must have
851 enough free memory so that if node1 fails, we can failover instance2
852 without any other operations (for reducing the downtime window). Let's
853 increase the memory of the current instances to 4G, and add three new
854 instances, two on node2:node3 with 8GB of RAM and one on node1:node2,
855 with 12GB of RAM (numbers chosen so that we run out of memory)::
857 node1# gnt-instance modify -B memory=4G instance1
858 Modified instance instance1
860 Please don't forget that these parameters take effect only at the next start of the instance.
861 node1# gnt-instance modify …
863 node1# gnt-instance add -t drbd -n node2:node3 -s 512m -B memory=8G -o debootstrap instance5
865 node1# gnt-instance add -t drbd -n node2:node3 -s 512m -B memory=8G -o debootstrap instance6
867 node1# gnt-instance add -t drbd -n node1:node2 -s 512m -B memory=8G -o debootstrap instance7
868 node1# gnt-instance reboot --all
869 The reboot will operate on 7 instances.
870 Do you want to continue?
880 Submitted jobs 677, 678, 679, 680, 681, 682, 683
881 Waiting for job 677 for instance1...
882 Waiting for job 678 for instance2...
883 Waiting for job 679 for instance3...
884 Waiting for job 680 for instance4...
885 Waiting for job 681 for instance5...
886 Waiting for job 682 for instance6...
887 Waiting for job 683 for instance7...
890 We rebooted instances for the memory changes to have effect. Now the
894 Node DTotal DFree MTotal MNode MFree Pinst Sinst
895 node1 1.3T 1.3T 32.0G 1.0G 6.5G 4 1
896 node2 1.3T 1.3T 32.0G 1.0G 10.5G 3 4
897 node3 1.3T 1.3T 32.0G 1.0G 30.5G 0 2
898 node1# gnt-cluster verify
899 Mon Oct 26 18:59:36 2009 * Verifying global settings
900 Mon Oct 26 18:59:36 2009 * Gathering data (3 nodes)
901 Mon Oct 26 18:59:37 2009 * Verifying node status
902 Mon Oct 26 18:59:37 2009 * Verifying instance status
903 Mon Oct 26 18:59:37 2009 * Verifying orphan volumes
904 Mon Oct 26 18:59:37 2009 * Verifying remaining instances
905 Mon Oct 26 18:59:37 2009 * Verifying N+1 Memory redundancy
906 Mon Oct 26 18:59:37 2009 - ERROR: node node2: not enough memory on to accommodate failovers should peer node node1 fail
907 Mon Oct 26 18:59:37 2009 * Other Notes
908 Mon Oct 26 18:59:37 2009 * Hooks Results
911 The cluster verify error above shows that if node1 fails, node2 will not
912 have enough memory to failover all primary instances on node1 to it. To
913 solve this, you have a number of options:
915 - try to manually move instances around (but this can become complicated
916 for any non-trivial cluster)
917 - try to reduce memory of some instances to accommodate the available
919 - if you have the ganeti-htools package installed, you can run the
920 ``hbal`` tool which will try to compute an automated cluster solution
921 that complies with the N+1 rule
926 In case a node has problems with the network (usually the secondary
927 network, as problems with the primary network will render the node
928 unusable for ganeti commands), it will show up in cluster verify as::
930 node1# gnt-cluster verify
931 Mon Oct 26 19:07:19 2009 * Verifying global settings
932 Mon Oct 26 19:07:19 2009 * Gathering data (3 nodes)
933 Mon Oct 26 19:07:23 2009 * Verifying node status
934 Mon Oct 26 19:07:23 2009 - ERROR: node node1: tcp communication with node 'node3': failure using the secondary interface(s)
935 Mon Oct 26 19:07:23 2009 - ERROR: node node2: tcp communication with node 'node3': failure using the secondary interface(s)
936 Mon Oct 26 19:07:23 2009 - ERROR: node node3: tcp communication with node 'node1': failure using the secondary interface(s)
937 Mon Oct 26 19:07:23 2009 - ERROR: node node3: tcp communication with node 'node2': failure using the secondary interface(s)
938 Mon Oct 26 19:07:23 2009 - ERROR: node node3: tcp communication with node 'node3': failure using the secondary interface(s)
939 Mon Oct 26 19:07:23 2009 * Verifying instance status
940 Mon Oct 26 19:07:23 2009 * Verifying orphan volumes
941 Mon Oct 26 19:07:23 2009 * Verifying remaining instances
942 Mon Oct 26 19:07:23 2009 * Verifying N+1 Memory redundancy
943 Mon Oct 26 19:07:23 2009 * Other Notes
944 Mon Oct 26 19:07:23 2009 * Hooks Results
947 This shows that both node1 and node2 have problems contacting node3 over
948 the secondary network, and node3 has problems contacting them. From this
949 output is can be deduced that since node1 and node2 can communicate
950 between themselves, node3 is the one having problems, and you need to
951 investigate its network settings/connection.
956 Since live migration can sometimes fail and leave the instance in an
957 inconsistent state, Ganeti provides a ``--cleanup`` argument to the
958 migrate command that does:
960 - check on which node the instance is actually running (has the
961 command failed before or after the actual migration?)
962 - reconfigure the DRBD disks accordingly
964 It is always safe to run this command as long as the instance has good
965 data on its primary node (i.e. not showing as degraded). If so, you can
968 node1# gnt-instance migrate --cleanup instance1
969 Instance instance1 will be recovered from a failed migration. Note
970 that the migration procedure (including cleanup) is **experimental**
971 in this version. This might impact the instance if anything goes
974 Mon Oct 26 19:13:49 2009 Migrating instance instance1
975 Mon Oct 26 19:13:49 2009 * checking where the instance actually runs (if this hangs, the hypervisor might be in a bad state)
976 Mon Oct 26 19:13:49 2009 * instance confirmed to be running on its primary node (node2)
977 Mon Oct 26 19:13:49 2009 * switching node node1 to secondary mode
978 Mon Oct 26 19:13:50 2009 * wait until resync is done
979 Mon Oct 26 19:13:50 2009 * changing into standalone mode
980 Mon Oct 26 19:13:50 2009 * changing disks into single-master mode
981 Mon Oct 26 19:13:50 2009 * wait until resync is done
982 Mon Oct 26 19:13:51 2009 * done
985 In use disks at instance shutdown
986 +++++++++++++++++++++++++++++++++
988 If you see something like the following when trying to shutdown or
989 deactivate disks for an instance::
991 node1# gnt-instance shutdown instance1
992 Mon Oct 26 19:16:23 2009 - WARNING: Could not shutdown block device disk/0 on node node2: drbd0: can't shutdown drbd device: /dev/drbd0: State change failed: (-12) Device is held open by someone\n
994 It most likely means something is holding open the underlying DRBD
995 device. This can be bad if the instance is not running, as it might mean
996 that there was concurrent access from both the node and the instance to
997 the disks, but not always (e.g. you could only have had the partitions
998 activated via ``kpartx``).
1000 To troubleshoot this issue you need to follow standard Linux practices,
1001 and pay attention to the hypervisor being used:
1003 - check if (in the above example) ``/dev/drbd0`` on node2 is being
1004 mounted somewhere (``cat /proc/mounts``)
1005 - check if the device is not being used by device mapper itself:
1006 ``dmsetup ls`` and look for entries of the form ``drbd0pX``, and if so
1007 remove them with either ``kpartx -d`` or ``dmsetup remove``
1009 For Xen, check if it's not using the disks itself::
1011 node1# xenstore-ls /local/domain/0/backend/vbd|grep -e "domain =" -e physical-device
1012 domain = "instance2"
1013 physical-device = "93:0"
1014 domain = "instance3"
1015 physical-device = "93:1"
1016 domain = "instance4"
1017 physical-device = "93:2"
1020 You can see in the above output that the node exports three disks, to
1021 three instances. The ``physical-device`` key is in major:minor format in
1022 hexadecimal, and 0x93 represents DRBD's major number. Thus we can see
1023 from the above that instance2 has /dev/drbd0, instance3 /dev/drbd1, and
1024 instance4 /dev/drbd2.
1026 .. vim: set textwidth=72 :
projects / ganeti-local / blob