On Fri, 12 May 2006, Erik Trimble wrote:
> I'm looking at using ZFS as our main file server FS over here.
>
> I can do the disk layout tuning myself, but what I'm more interested in
> is getting thoughts on the amount of RAM that might help performance on
> these machines. Assume I've got more than enough network and disk
> bandwidth, and the disks are JBODs, so there is no NVRAM or anything
> else on the arrays.
>
> The machines will be doing NFS and AFS filesharing ONLY, so this
> discussion is relevant to ZFS as a fileserver, with no other
> considerations.
>
>
> Now, there are three usage patterns (I'm interested in tuning for each
> scenario, as they probably will be separate machines):
>
>
> (A) random small read (80%)/ small write (20%) - files in the sub 1MB
> size, usually in the 50-200kB size
>
> (B) sequential small read (80%) / small write (20%) - e.g. copy the
> entire contents of directories around. Files in mid-100k range, copying
> 10s of MB total at a time.
>
> (C) random read/write inside a single file (e.g. database store) - file
> is under 10GB or so.
>
>
> I'm assuming that ZFS read-ahead benefits greatly by more RAM for (A),
> but I'm less sure about the other two cases, and I'm not sure at all
> about how more RAM helps write performance (if at all).
Eric, I'll give you a generic answer to your generic question - given that
there is a lack of specifics on both the question and answer side of the
equation! IMHO you absolutely need to be running the target platform(s)
in 64-bit mode. There will ensure that there is sufficient kernel memory
available for ZFS in the Update 2 release.
Secondly, my recommendation for the "sweet spot", in terms of system
memory is 4Gb - or more. With 4Gb, ZFS performance is very, very nice.
This personal opinion is from my hands-on eval/testing.
> Ideas? Point me to docs?
This answer would fall under the "ideas" category! :)
In terms of docs, the only other point of reference is that RAIDZ systems
should be composed of a single digit number of disk drives, between 3
(minimum) and 9 (maximum). So choose the disk drive size to provide the
memory pool size (IOW capacity) you need for your application user
community. Or form multiple pools to satisfy your storage requirements.
Remember that this is the first production release of zfs. While I'm very
confident of the world class capabilities/talent of the zfs development
team ... you can't compare zfs, in terms of absolute reliability, with an
alternative filesystem (like UFS) that has millions & millions of hours of
accumulated usage across a very broad set of application problem domains.
So plan for the occasional glitch/bug. IOW - don't put all your
filesystem "eggs" in one "basket" - and don't operate without a "safety
net".
I would whole-heartly recommond zfs for your production environment. The
upside is so much ahead of any perceived downsides - and the performance,
ease of use, capabilities etc as so far ahead of UFS that it'll simply
blow you away.
Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED]
Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT
OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005
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