Re: Oracle RAC & Fusion I/O Cards

From: Jakub Wartak <vnulllists_at_pcnet.com.pl>
Date: Sun, 31 Jan 2010 13:36:05 +0100
Message-Id: <201001311336.05421.vnulllists_at_pcnet.com.pl>

Dnia sobota, 30 stycznia 2010 02:07, Thomas Roach napisał:
> I have a RAC (10.2.0.4 on RHEL 5.3 Linux x86-64) cluster and we do a large
> amounts of sorts and things in Parallel. I was looking at Fusion I/O cards
> which are kept in the server. What I was thinking was, if I used a
> Temporary Tablespace Groups and assigned users to this, would it be
> possible to store 1 temporary tablespace locally on each node (4 total), or
> does this have to be on shared storage as well? If I can store them local,
> then I can use the Fusion I/O device.

Thomas,
There is silence on this topic, so perhaps I'll try...

If you have single schema (and tablespace assigment is done on per-schema level) you would need to create users schemaN (where N=RAC_node_id). This would require proper GRANTs on schemaN to access orginal "schema"... Then you would need to perform temp. tablespaces assigment to schemaN. AFAIK temporary tablespace in 10.2 was not registered in controlfiles.

.. but first I would start from measuring I/O performance of current tempfiles. There are many ways:
1) gv$filestat
2) assigning dedidcated shared storage location (CFS/LUN) and placing only tempfiles there to monitor their real I/O metrics via iostat -x 3) systemtap (might be difficult on RHEL5.3)

I would be very worried about several things: 1) RAC access to tempfile from other RAC node especially during things like TAF SELECT failovers (not sure how TAF does this interally, by re-executing whole query from start and starting returning rows from last sent row?) 2) Load balancing... i mean: ensuring that only schemaN on nodeN can access tempfileN but no tempfileM (where N,M = instance IDs), what might be the problem is that during instanceN crash, clients would start to failover to instanceM (using schemaN which would have been configured to use tempfileN).

So taking into account "2", if you have 3 nodes each FusionI/O filesystem would need to have same tempfiles configured (?)

For me it is RISKY, i would just stick to tuning PGA/adding more memory*/putting more NVRAM into storage :)

• = if don't have some large ammounts of it like 128GB.

-- 
Jakub Wartak
http://jakub.wartak.pl/blog
--
http://www.freelists.org/webpage/oracle-l

Received on Sun Jan 31 2010 - 06:36:05 CST