Messages in this thread | | | Date | Wed, 25 Mar 2009 11:26:57 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: Linux 2.6.29 |
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On Wed, 25 Mar 2009, Linus Torvalds wrote: > > Even a suck-ass laptop drive can write streaming data fast enough that > people don't care. The problem is invariably that writes from different > sources (much of it being metadata) interact and cause seeking.
Actually, not just writes.
The IO priority thing is almost certainly that _reads_ (which get higher priority by default due to being synchronous) get interspersed with the writes, and then even if you _could_ be having streaming writes, what you actually end up with is lots of seeking.
Again, good SSD's don't care. Disks do. It doesn't matter if you have a FC disk array that can eat 300MB/s when streaming - once you start seeking, that 300MB/s goes down like a rock. Battery-protected write caches will help - but not a whole lot when streaming more data than they have RAM. Basic queuing theory.
Linus
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