Messages in this thread | | | Date | Wed, 16 Jan 2008 00:15:03 +0000 | From | Alan Cox <> | Subject | Re: [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck) |
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> 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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