On 03/08/11 22:15, Gary R. Schmidt wrote:
> On Wed, March 9, 2011 12:22, Phil Stracchino wrote:
> [SNIP]
>> Now, I said I'd get back to the MySQL issues.  I was reading through
>> some documents about mySQL on ZFS, and came across (again) a
>> recommendation from one MySQL tester that reported the best MySQL
>> performance from setting the InnoDB buffer pool small, 100MB or so, and
>> allowing ZFS to do the data caching.  And I thought, "You know, I don't
>> believe I've ever tried this.  I'll give it a shot and see how it goes."
>>
>> Well, after trying this, I can now definitively state:  DO NOT DO THIS
>> IF YOUR BACULA CATALOG IS ON MYSQL.  It may well work well for general
>> usage, but for Bacula, this configuration trick DOES NOT WORK.  If you
>> are using Bacula with a MySQL catalog database on ZFS, configure MySQL
>> as you would if it were NOT on ZFS.  Do NOT rely on the "let ZFS cache
>> the data" trick, because it won't work with Bacula.
>>
> Hmm, what version of MySQL did the document you found refer to?  And what
> one are you using?

5.5, and 5.5, in both cases.

> It is possible that the recommendation is correct for the webstack or some
> internal SUN build of MySQL - my Webstack has "innodb_buffer_pool_size =
> 2048M" - perhaps it is correct when using the MyISAM engine?  Or some such
> variant?

I'm using all InnoDB.  There is almost no real-world case these days in
which MyISAM is the Right Engine.

> The only MySQL on ZFS recommendation I can remember reading was the one to
> change the record size of the underlying file system where the INNODB data
> files reside to 16K, nothing about buffer pool sizes.

Yup. zfs set recordsize.  That comes in because innoDB writes in 16k chunks.


> That said, after far too many years writing, administering, and using
> databases, the thought of using a small buffer pool (or equivalent) on
> *any* database just doesn't feel right to me.

Same here.  But I figured I'd try it once.  NOT good at all.


-- 
  Phil Stracchino, CDK#2     DoD#299792458     ICBM: 43.5607, -71.355
  alaric AT caerllewys DOT net   alaric AT metrocast DOT net   phil AT 
co.ordinate DOT org
  Renaissance Man, Unix ronin, Perl hacker, SQL wrangler, Free Stater
                 It's not the years, it's the mileage.

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