[CentOS] Re: Hard disk recomendation for a software raid 5 array. Does Linux Software Raid support/interacts well with TLER enabled disks.

Scott Silva ssilva at sgvwater.com
Fri Jul 27 17:19:59 UTC 2007

Alexander Georgiev spake the following on 7/27/2007 5:32 AM:
> Hi people,
> I am building a cheap remote rsync backup server using a software raid
> 5 array of 4 500GB disks. What I have available on the market is:
> 1. HITACHI GST Deskstar T7K500 500GB 7200rpm 16MB cache Serial ATA II-300
> 2. SEAGATE Barracuda 7200.10 with NCQ 500GB 7200rpm 16MB cache Serial ATA II-300
> 3. Western Digital 500GB SATAII RAID EDITION Caviar SE16 7200rpm 8.9ms
> 16MB cache
> I  am tempted to use the Western Digital Raid Edition as it has 5
> years of warranty. However I found out that the "Raid Edition" means
> that the disk supports TLER - time limited error recovery:
> http://www.excelmeridiandata.com/products/wd_raid_edition_drive.shtml
> A more profound description can be found here
> http://www.wdc.com/en/library/sata/2579-001098.pdf.
> In summary, the error recovery time of the hard disk is reduced to 8
> second. If the hard disk cannot perform the recovery it will report an
> error to the RAID controller and delegate the recovery to the
> controller.
> As I intend to use linux software raid on Centos 5, I will not have a
> RAID controller to deal with this delegated error, but two cheap  I/O
> SATA controllers.
> Has anybody used 'raid edition' disks with software raid?
> Does anybody know how linux software raid interacts/supports these TLER disks.
> Best regards
> Alex
I have used raid aware and non-raid aware disks for both hardware and software
raid. You really want the raid edition drives, as they will send a fail up the
channel much faster than a non-raid drive. The non-raid drives will retry over
and over, and you stand a chance of data loss while they decide what to do.
Software raid will just fail the drive and switch to degraded mode.


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