Re: SSA vs SCSI - general IO troubleshooting
From: Hunter, Mark (Mark.Hunter_at_ANHEUSER-BUSCH.COM)
Date: 03/24/05
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Date: Thu, 24 Mar 2005 11:09:17 -0600 To: aix-l@Princeton.EDU
What version of AIX are you running? What version of Oracle? What size drives?
Which SSA adapter? jfs or jfs2? INLINE logs or shared log lv?
We run AIX 5.2 with Oracle 9I. Our rule of thumb for our sized databases is 1GB
of RAM per database instance. Oracle 8.1.7 used much less.
Oracle performance is very memory sensitive. What are your min and maxperm set
to? For aix 5.2, run vmo -a | grep %
If the box does nothing but oracle, you should probably have values similar to
minperm% = 10
maxperm% = 20
maxclient% = 20
If you are running 5.2, you can use lvmstat to find hot logical volumes.
As usual, the application should be reviewed for sub optimal code.
Mark Hunter
Anheuser-Busch Cos.
MIS Consultant, ES&SO Server Planning and Integration
*Office: (314) 632-6663
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*Email: Mark.Hunter@Anheuser-Busch.com
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From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of Mark
Schlechte
Sent: Thursday, March 24, 2005 10:46 AM
To: aix-l@Princeton.EDU
Subject: SSA vs SCSI - general IO troubleshooting
I'm trying to figure out what kind of performance differences there are between
good ol SSA compared to some SCSI Ultra 320 disks or even if that is my problem.
Server A is a 6-way 6F1 668MHZ, 8GB ram with a number of internal SSA disks and
13 oracle databases.
The disk is a mix of some RAID5, and RAID1 over 2 adapters.
Server B is a 2-way 6C3 1.2GHZ, 2GB ram with 6 SCSI disks and 4 oracle
databases.
This disk is just JBOD using a single 6203 SCSI adapter.
Due to oracle licensing costs we are moving one of the databases off the 6F1
onto the 2-way 6C3.
Our testing indicates very high I/O rates on the SCSI disk and tasks take way to
long to complete.
I'm wondering where I should focus my effort on trying to aleviate the disk I/O
bottleneck.
Is it SSA vs SCSI, the adapter (cache on the SSA adapter), more memory, should I
look at vmtune settings, etc.
I did run filemon while testing was going on.
CPU utilization is 67.7%
Most active Segments (all page table entries)
Most Active Physical Volumes (all hdisks show util 1.00)
Lots of questions I know, just looking for any general comments on where people
would start first.
Mark
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- Previous message: Patrick B. O'Brien: "Re: SSA vs SCSI - general IO troubleshooting"
- Maybe in reply to: Mark Schlechte: "SSA vs SCSI - general IO troubleshooting"
- Next in thread: Chafik,Basim: "Re: SSA vs SCSI - general IO troubleshooting"
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