Messages in this thread | | | Date | Sun, 16 Aug 2009 18:51:23 -0400 | From | Mark Lord <> | Subject | Re: Discard support |
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Theodore Tso wrote: > On Sun, Aug 16, 2009 at 02:50:40PM -0700, Roland Dreier wrote: >> > Well, yes and no ... a lot of SSDs don't actually implement NCQ, so the >> > impact to them will be less ... although I think enterprise class SSDs >> > do implement NCQ. >> >> Really? Which SSDs don't implement NCQ? > > The Intel X25-M was the first SSD to implement NCQ. The OCZ Core V2 > advertised NCQ with a queue depth of 1, but even that was buggy, so > Linux has a black list for the that SSD: > > http://markmail.org/message/jvjpmcdqjwrmyl4w > > As far as I know, all of the SSD's using the crappy JMicron JMF602 > controllers don't support NCQ in any real way, which would includes > most of the reasonably priced SSD's up until first half of this year. > (The OCZ Summit SSD, which uses the Indilnx controller is an exception > to this statement, but it's more expensive that the JMF602 based > SSD's, although less expensive than the Intel SSD.) > > JMicron is trying to seek redemption with their JMF612 controllers, > which were announced at the end of May of this year, and those > controllers do support NCQ, and are claimed to not to have the > disatrous small write latency problem of their '602 bretheren. I'm > not aware of any products using the JMF612 yet, though. (According to > reports the '612 controllers weren't going to hit mass production > until July, so hopefully later this fall we'll start seeing products > using the new JMicron controller.) ..
Great summary, Ted.
To add: SSDs based upon the Indilinx controller don't appear to scale beyond an NCQ depth of about 4 or so. Whereas Intel SSDs continue to improve with increased queue depth up to 31 on Linux.
Or at least that's what I recall from reading various SSD benchmarks a few weeks ago here.
Cheers
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