[Gllug] Centos 5.6 3ware raid 5

Karanbir Singh mail-lists at karan.org
Wed Feb 8 21:03:23 UTC 2012

On 02/08/2012 04:47 PM, Ken Smith wrote:
> 05:04.0 RAID bus controller: 3ware Inc 7xxx/8xxx-series PATA/SATA-RAID
> (rev 01)
>     Subsystem: 3ware Inc 7xxx/8xxx-series PATA/SATA-RAID

This looks to be a 3ware 8006 series interface... lspci -n; will give
you the device id. and you can verify that.

These were not the fastest cards in the word, the powerpc chips
introduced in the 9500 and beyond made a massive difference to raid5
performance; although they should still not be any slower than an
onboard sata interface, if you compare like for like.

Also, the filesystem you use can be an issue - I've heard anecdotal
feedback that xfs on these 3w cards was a better match than ext3 in
radi5; and getting the block alignment right was super critical since
the 3w bios tries some funky stuff under the hood.

finally.. a 3 disk raid 5 is most likely going to be slower than a 3
disk raid10 with 1 mirror missing. Either way you lose a disk and its
restore-from-backup situation.

You can also try tweaking the write-back cache and sync settings.

If all that has no real impact, then yeah jbod the 3 500gb disks, and
mdraid them on the OS.

Karanbir Singh
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