Jason,
Jason J. W. Williams wrote:
Hi Robert,
We've got the default ncsize. I didn't see any advantage to increasing
it outside of NFS serving...which this server is not. For speed the
X4500 is showing to be a killer MySQL platform. Between the blazing
fast procs and the sheer number of spindles, its perfromance is
tremendous. If MySQL cluster had full disk-based support, scale-out
with X4500s a-la Greenplum would be terrific solution.
At this point, the ZFS memory gobbling is the main roadblock to being
a good database platform.
Regarding the paging activity, we too saw tremendous paging of up to
24% of the X4500s CPU being used for that with the default arc_max.
After changing it to 4GB, we haven't seen anything much over 5-10%.
Remember that ZFS does not use the standard solaris paging architecture
for caching.
Instead it uses ARC for all its caching. And that is the reason tuning
the ARC should
help in your case.
The zio_bufs that you referred to in the previous are the caches used by
ARC for caching
various things (including the metadata and the data).
Thanks and regards,
Sanjeev.
Best Regards,
Jason
On 1/10/07, Robert Milkowski <[EMAIL PROTECTED]> wrote:
Hello Jason,
Thursday, January 11, 2007, 12:36:46 AM, you wrote:
JJWW> Hi Robert,
JJWW> Thank you! Holy mackerel! That's a lot of memory. With that
type of a
JJWW> calculation my 4GB arc_max setting is still in the danger zone
on a
JJWW> Thumper. I wonder if any of the ZFS developers could shed some
light
JJWW> on the calculation?
JJWW> That kind of memory loss makes ZFS almost unusable for a
database system.
If you leave ncsize with default value then I belive it won't consume
that much memory.
JJWW> I agree that a page cache similar to UFS would be much better.
Linux
JJWW> works similarly to free pages, and it has been effective enough
in the
JJWW> past. Though I'm equally unhappy about Linux's tendency to grab
every
JJWW> bit of free RAM available for filesystem caching, and then cause
JJWW> massive memory thrashing as it frees it for applications.
Page cache won't be better - just better memory control for ZFS caches
is strongly desired. Unfortunately from time to time ZFS makes servers
to page enormously :(
--
Best regards,
Robert mailto:[EMAIL PROTECTED]
http://milek.blogspot.com
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