Re: [Patch] document ext3 requirements (was Re: [RFD] Incrementalfsck)

[Alan Cox]

> Writeback cache on disk in iteself is not bad, it only gets bad if the
> disk is not engineered to save all its dirty cache on power loss,
> using the disk motor as a generator or alternatively a small battery.
> It would be awfully nice to know which brands fail here, if any,
> because writeback cache is a big performance booster.

AFAIK no drive saves the cache. The worst case cache flush for drives is
several seconds with no retries and a couple of minutes if something
really bad happens.

This is why the kernel has some knowledge of barriers and uses them to
issue flushes when needed.
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