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

Ric Wheeler
2007-03-31T12:56:06Z

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