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.TH zcav 8
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.SH "NAME"
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zcav \- program to test raw hard drive throughput.
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.SH "SYNOPSIS"
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.B zcav
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.I [\-b block\-size[:chunk\-size]] [\-c count] [\-n num_blocks] [\-w]
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.I [\-u uid\-to\-use:gid\-to\-use] [\-g gid\-to\-use]
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.I [\-f] file\-name
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.SH "DESCRIPTION"
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This manual page documents briefly the
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.BR zcav ,
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program.
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.P
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Modern hard drives have a constant rotational speed but have varying numbers
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of sectors per track (outside tracks are longer and have more sectors). This
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is referred to as Zoned Constant Angular Velocity (or ZCAV). The outer tracks
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will have a higher data transfer rate due to having more sectors per track,
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these tracks generally have the lower track/sector numbers.
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.P
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This program tests the ZCAV performance of a hard drive, by reading the entire
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data on it a specified number of times. The file name given as the first
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parameter, it can be specified as
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.BR \- ,
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for standard input. This file will be opened as read\-only and in usual
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operation it will be
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.BR /dev/hdX
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or
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.BR /dev/ide/host0/busX/targetY/lun0/disc
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depending on whether you use devfs or not (NB operating systems other than
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Linux will have different device names).
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.P
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The output should be able to be easily graphed with
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.BR gnuplot
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which is what I use to view the results.
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.SH "OPTIONS"
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.TP
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.B \-b
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the size (in Meg) of the blocks to read/write (default 100M), optionally
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followed by a ':' and the chunk size for read/write operations (default 1M).
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Note that the chunk size must be less than or equal to the block size and
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must also be significantly less than the size of the RAM in the machine.
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Also note that for the write test there will be a fsync() after writing every
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chunk.
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.TP
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.B \-c
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the number of times to read/write the entire disk.
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.TP
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.B \-n
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the amount of data (in Meg) to read/write on each pass (default the entire device).
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.TP
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.B \-f
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the file\-name for the input data. This isn't needed on well configured
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systems that have a recent Glibc where you can specify the file name without
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the \-f flag.
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.TP
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.B \-u
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user\-id to use.  When running as root specify the UID to run the tests as, it
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is not recommended to use root, so if you want to run as root use
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.B \-u root.
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Also if you want to specify the group to run as then use the
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.B user:group
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format.  If you specify a user by name but no group then the primary group of
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that user will be chosen.  If you specify a user by number and no group then
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the group will be
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.B nogroup.
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.TP
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.B \-g
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group\-id to use.  Same as using
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.B :group
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for the
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.B \-u
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parameter, just a different way to specify it for compatibility with other
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programs.
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.TP
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.B \-w
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write zero blocks to the disk instead of reading from the disk - will destroy data!
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.SH "AUTHOR"
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This program, it's manual page, and the Debian package were written by
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Russell Coker <russell@coker.com.au>.
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.SH "AVAILABILITY"
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The source is available from http://www.coker.com.au/bonnie++ .
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.P
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See http://etbe.coker.com.au/category/benchmark for further information.