ZFS FAQ (Was: SSD recommendations for ZFS cache/log)

[Charles Sprickman]

On Nov 19, 2012, at 11:05 PM, Eitan Adler wrote:

> On 16 November 2012 13:41, Eitan Adler <eadler at freebsd.org> wrote:
>> On 15 November 2012 23:58, Stephen McKay <smckay at internode.on.net> wrote:
>>> On Thursday, 15th November 2012, Eitan Adler wrote:
>>> 
>>>> Can people here please tell me what is wrong in the following content?
>>> 
>>> A few things.  I'll intersperse them.
>>> 
>>>> Is there additional data or questions to add?
>>> 
>>> The whole ZFS world desperately needs good documentation.  There
>>> are misconceptions everywhere.  There are good tuning hints and
>>> bad (or out of date) ones.  Further, it depends on your target
>>> application whether the defaults are fairly good or plain suck.
>> 
>> New version of the patch taking into account the comments so far:
>> 
>> http://people.freebsd.org/~eadler/files/add-zfs-faq-section.diff
> 
> Thanks for all the comments, private and public. I've committed a
> modified version of the above.

Wonderful to see some work on this.

One of the great remaining zfs mysteries remains all the tunables
that are under "vfs.zfs.*".  Obviously there are plenty of read-only
items there, but conflicting information gathered from random forum
posts and commit messages exist about what exactly one can do
regarding tuning beyond arc sizing.

If you have any opportunity to work with the people who have ported
and are now maintaining zfs, it would be really wonderful to get
some feedback from them on what knobs are safe to twiddle and why.
I suspect many of the tunable items don't really have meaningful
equivalents in Sun's implementation since the way zfs falls under
the vfs layer in FreeBSD is so different.

Thanks,

Charles

> 
> -- 
> Eitan Adler
> Source, Ports, Doc committer
> Bugmeister, Ports Security teams
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