Messages in this thread | | | Date | Thu, 03 Sep 2009 09:50:43 -0400 | From | Ric Wheeler <> | Subject | Re: raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) |
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On 09/03/2009 09:34 AM, Krzysztof Halasa wrote: > Ric Wheeler<rwheeler@redhat.com> writes: > >>>> Just to add some support to this, all of the external RAID arrays that >>>> I know of normally run with write cache disabled on the component >>>> drives. >>> >>> Do they use "off the shelf" SATA (or PATA) disks, and if so, which ones? >> >> Which drives various vendors ships changes with specific products. >> Usually, they ship drives that have carefully vetted firmware, etc. >> but they are close to the same drives you buy on the open market. > > But they aren't the same, are they? If they are not, the fact they can > run well with the write-through cache doesn't mean the off-the-shelf > ones can do as well.
Storage vendors have a wide range of options, but what you get today is a collection of s-ata (not much any more), sas or fc.
Some times they will have different firmware, other times it is the same.
> > Are they SATA (or PATA) at all? SCSI etc. are usually different > animals, though there are SCSI and SATA models which differ only in > electronics. > > Do you have battery-backed write-back RAID cache (which acknowledges > flushes before the data is written out to disks)? PC can't do that.
We (red hat) have all kinds of different raid boxes...
ric
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