Re: Why is NCQ enabled by default by libata? (2.6.20)

From: Ric Wheeler
Date: Sat Mar 31 2007 - 08:56:26 EST




Mark Rustad wrote:
On Mar 27, 2007, at 1:38 PM, Jeff Garzik wrote:

Mark Rustad wrote:
reorder any queued operations. Of course if you really care about your data, you don't really want to turn write cache on.

That's a gross exaggeration. FLUSH CACHE and FUA both ensure data integrity as well.

Turning write cache off has always been a performance-killing action on ATA.

Perhaps. Folks I work with would disagree with that, but I am not enough of a storage expert to judge. My statement mirrors the judgement of folks I work with that know more than I do.

You can easily demonstrate that disabling write cache on a S-ATA or ATA drive will drop your large file write performance by 50% - just try writing 10MB files to disk.

ric


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