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Full Discussion: Raid0 array stresses only 1 disk out of 3
Top Forums UNIX for Dummies Questions & Answers Raid0 array stresses only 1 disk out of 3 Post 302970828 by hicksd8 on Tuesday 12th of April 2016 08:57:29 AM
Old 04-12-2016
RAID0 "stripes" the data across the three actuators you have and the stripe size (that's official RAID speak) is the minimum allocation. So if the stripe is 2k then the first 2k bytes of a file is written to the first drive, the next 2k to the second drive, and the third 2k to the third drive. It then goes back to the first drive, and so on.

So it's not difficult to see that writing lots of small files will give unpredictable results respecially if they're less than 2k each. Also, read requests can only be satisfied be reading the drive(s) where the files were written.

So your results are misleading.

If you have a desire to test this then you need to do something like......
Create a 4GB file on (ideally) an internal drive not part of this RAID0 array. Kick all the users off if you can and then copy this 4GB to the RAID filesystem and take your measurements whilst that's going on. It won't be precise but should give you a better set of figures.
 

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LEARN ABOUT HPUX

vxr5check

vxr5check(1M)															     vxr5check(1M)

NAME

       vxr5check - verify RAID-5 volume parity

SYNOPSIS

       /etc/vx/bin/vxr5check [-i | -v] [-g diskgroup] volume

DESCRIPTION

       The vxr5check utility compares the parity of each stripe of a RAID-5 volume specified by volume.  vxr5check reads the data for each stripe,
       generates the parity for this stripe, and compares this parity with the existing parity.

       vxr5check can be run against the entire RAID-5 volume, or incrementally on RAID-5 stripe boundaries, by specifying the -i option.

OPTIONS

       -g diskgroup
		 Specifies the Veritas Volume Manager (VxVM) disk group name for the RAID-5 volume name for verification.  If this option  is  not
		 specified, the default disk group is determined using the rules given in the vxdg(1M) manual page.

       -i	 Verifies the RAID-5 volume incrementally per stripes.	If a parity mismatch is found, that stripe location is displayed.

       -v	 Verbose output for the incremental vxr5check verification.  The verbose option outputs each stripe number that is being verified.

OUTPUT FORMAT

       In  verbose  mode and incremental mode, summary reports for each stripe of the RAID-5 volume are printed in output records.  If an error is
       returned for a stripe, then an error message and stripe number are displayed.  In non-verbose mode, if an error is returned, an error  mes-
       sage is displayed.

       If a parity mismatch error is determined on a stripe, vxr5check exits on that stripe and does not continue for the remaining stripes in the
       RAID-5 volume.

FILES

       /usr/lib/vxvm/bin/vxr5vrfy    The utility that vxr5check calls to perform RAID-5 parity verification operations for  the  specified  RAID-5
				     volume.

EXIT CODES

       The  vxr5check  utility exits with a non-zero status if the attempted operation fails.  A non-zero exit code is not a complete indicator of
       the problems encountered, but rather denotes the first condition that prevented further execution of the utility.

       See vxintro(1M) for a list of standard exit codes.

NOTES

       Do not run vxr5check on a volume that is in degraded mode.

SEE ALSO

       vxevac(1M), vxintro(1M), vxmend(1M), vxvol(1M)

VxVM 5.0.31.1							    24 Mar 2008 						     vxr5check(1M)
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