Hi Jeremy,

 

if you buy a PAM card for one of your controllers you always should buy one for the other controller too. It will speed up your Oracle random reads at normal operation as well as help you facing a performance problem if the filesystem/VM- controller with the PAM card fails and your database controller has to handle all your IO.

 

PAM is short for Performance Accelerator Modul. There are two flavours: PAM-I and PAM-II. PAM-II is of greater cache size but has a slower access time than PAM-I. As far as I know PAM-II is not supported with your version of DataONTAP but please check this with NetApp.

 

You may send your flexscale-pcs statistics to NetApp (perhaps with a perfstat).  They can analyze this and tell you what PAM card would best fit to your IO profile or if you best add more spindles. Furthermore they can help you with your Oracle performance issue.

 

Regarding your Oracle performance issues:

It may be helpful to check if you encounter the performance issue only in your database instances or if your host filesystem in the LUN is slow too. For this you can use “dd” (on UNIX) to generate a serial write or read IO on your LUN. You may test with different block sizes. Please be sure to include the blocksize of your Oracle instance in the tests. Well, I know that nobody (especially NetApp) likes dd to test performance of a LUN. But it’s easy to use, always at hand and my experience is that if dd is slow other performance is not very much better.

If your performance without Oracle is acceptable (what I expect) then you can look at the Oracle SGA. Increasing this may help to cache more data on your host and decrease IO. You should analyze your select statements, too. If you see a lot of full table scans then you can use indexes to avoid those. But for this you best have an Oracle DBA at hand.

 

Best Regards

 

 

 

i. A. Dipl.-Inform. (FH) Walter J. Kießl

 

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Von: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] Im Auftrag von Page, Jeremy
Gesendet: Montag, 22. Februar 2010 21:38
An: Romeo Theriault
Cc: toasters@mathworks.com
Betreff: (WARNING!!! S/MIME with incorrect signature) RE: PAM cards or disks and some questions about the impact of running with PAM

 

I've checked the latency on both the host side (nmon) and at the disk level (statit). I am pretty sure they are ok, reads never go higher than 4ms and writes are in the 1ms range (on disk) and from the AIX side it's not much worse except for a few specific file systems. I want the PAM  II cards for my VMs and shares (other controller) more than Oracle but I wanted to make sure I was not missing a glaring IO problem on the DB side before I got something that does not make any difference for writes.

 

The SATA disks holding my VMs are crying out for PAM relief and like you said it won't (shouldn't) hurt for Oracle. I want to make sure that I am doing due dilligance (as far as I can with out access to the data on the Oracle side anyways) so the folks who I provide storage to are comfortable I am making the right choice.

 

Thanks for all the feedback, I am learning a lot which is always good.

 

From: Romeo Theriault [mailto:romeotheriault@gmail.com]
Sent: Monday, February 22, 2010 1:39 PM
To: Page, Jeremy
Cc: toasters@mathworks.com
Subject: Re: PAM cards or disks and some questions about the impact of running with PAM

 

On Tue, Feb 23, 2010 at 1:35 AM, Page, Jeremy <jeremy.page@gilbarco.com> wrote:

I read that, unfortunately I am not at 7.3.2 yet, I do get the counters but the format is a bit old.

 

My disk utilization rarely goes above 25%

 

Here's what I see but since I'm not at 7.3.2 the numbers may be misleading, I don't know.

array01*> stats show -p flexscale-pcs
Instance    Blocks Usage   Hit  Miss Hit Evict Invalidate Insert

---
     ec0   4194304    90 11733  3479  77  1748         57   2236
     ec1   4194304    38  1203  2275  34   343        401   1748


I'm by no means an expert on any of this and it's the first time I really look at PCS data but it certainly seems like at least the first level of cache (ec0) would help things out with a 90% usage and 11,733 hits but on the other hand a max 25% disk utilization doesn't seem very high to me. You also mentioned to me that your cache age is a fairly good size too. So, I'm not really sure. It certainly doesn't seem like a PAM card would hurt, that's for sure.

If the only thing noticing a performance issue is the Oracle DB you might want to look at the latency on those volumes.

stats show -i 3 volume:*:avg_latency

or using Performance Advisor.

Romeo


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