Re: raid is dangerous but that's secret (was Re: [patch] ext2/3:document conditions when reliable operation is possible)

From: david
Date: Thu Sep 03 2009 - 10:36:24 EST

On Thu, 3 Sep 2009, Krzysztof Halasa wrote:

Ric Wheeler <rwheeler@xxxxxxxxxx> 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

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.

frequently they are exactly the same drives, with exactly the same firmware.

you disable the write caches on the drives themselves, but you add a large write cache (with battery backup) in the raid card/chassis

Are they SATA (or PATA) at all? SCSI etc. are usually different
animals, though there are SCSI and SATA models which differ only in

it depends on what raid array you use, some use SATA, some use SAS/SCSI

David Lang
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