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Ask the Expert: Performance Calculations on Clariion/VNX
Performance calculations on the CLARiiON/VNX with RRR & Jon Klaus
Welcome to the EMC Support Community Ask the Expert conversation. This is an opportunity to learn about Performance calculations on the Clariion /VNX systems and the various considerations that must be taken into account
This discussion begins on Monday, August 13th. Get ready by bookmarking this page or signing up for email notifications.
Your hosts:
Rob Koper is working in the IT industry since 1994 and since 2004 working for Open Line Consultancy. He started with Clariion CX300 and DMX-2 and worked with all newer arrays ever since, up to current technologies like VNX 5700 and the larger DMX-4 and VMAX 20k systems. He's mainly involved in managing and migrating data to storage arrays over large Cisco and Brocade SANs that span multiple sites widely spread through the Netherlands. Since 2007 he's an active member on ECN and the Support Forums and he currently holds Proven Professional certifications like Implementation Engineer for VNX, Clariion (expert) and Symmetrix as well as Technology Architect for Clariion and Symmetrix.
Jon Klaus has been working at Open Line since 2008 as a project consultant on various storage and server virtualization projects. To prepare for these projects, an intensive one year barrage of courses on CLARiiON and Celerra has yielded him the EMCTAe and EMCIEe certifications on CLARiiON and EMCIE + EMCTA status on Celerra.
Currently Jon is contracted by a large multinational and part of a team that is responsible for running and maintaining several (EMC) storage and backup systems throughout Europe. Amongst his day-to-day activities are: performance troubleshooting, storage migrations and designing a new architecture for the Europe storage and backup environment.
This event ran from the 13th until the 31st of August .
Here is a summary document og the higlights of that discussion as set out by the experts. Ask The Expert: Performance Calculations on Clariion/VNX wrap up
The discussion itself follows below.
RRR
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August 16th, 2012 06:00
If you don't need the IOps RAID5 isn't that bad at all. I've even seen log disks that were several hundred GBs in size compared to the db disk which was perhaps 200GB bigger than the log disk, so you simply can't say 1 size fits all. If you don't have bottlenecks now, check (perfmon for example) how many read and write operations as well as the R/W ratio you have.
bartdonders
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August 16th, 2012 06:00
That's what they told me...
Without this knowledge, I was thinking that FAST Cache could end the discussion about RAID level for log disks... But unfortunately ;-)
RRR
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August 16th, 2012 06:00
Hmmmmm, I'm not aware that FAST Cache should be disabled on the log LUNs. I would expect FAST Cache to be really helpful there as it absorbs excessive writes from RAM cache to EFD drives instead of the slower rotating drives.
Let's check if anyone can help us here: does FAST Cache need to be disabled on LUNs that are used for database logging?
dynamox
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August 16th, 2012 06:00
i also heard a little blurb at EMC World that 5.32 should have enhancements where they detect sequential patterns and don't promote them to Fast Cache.
RRR
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August 16th, 2012 07:00
Ok, avoid RAID5, but that's in an ideal world. I think that calculating the requirements are always better.
RRR
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August 16th, 2012 07:00
That would be wonderful and a real enhancement since then you don't have to worry about either dis- or enabling FAST Cache!
RRR
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August 16th, 2012 07:00
I know…. These were high I/O OLTP of a University Hospital and they wanted to make sure the transactions were saved (for 2 days I think it was) even without the hourly backup.
RRR
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August 16th, 2012 07:00
Exactly, that’s why I asked… Glad Dynamox came to the rescue!
dynamox
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August 16th, 2012 07:00
if you are going to dedicate one raid group for specific server, probably yes. But considering how small redo log files are, storage admins like to put multiple server's redo log files on the same RG/Pool. So multiple sequential streams become random writes as far as RG/Pool is concerned. Agree ?
dynamox
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August 16th, 2012 07:00
50% of DB ? That's insane, none of my multi-terabyte OLTP databases have redo logs that take up 50% of the database size.
dynamox
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August 16th, 2012 07:00
you are not confusing redo logs and archive logs ?
RRR
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August 16th, 2012 07:00
Like I said before, redo logs don't have to be small: I've seen db servers with database drives of 500GB and redo log drives of 250GB !!!!
JonK1
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August 16th, 2012 07:00
Agreed dynamox, good point!
dynamox
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August 16th, 2012 07:00
8.2.3.2 Redo Log Files
If the high-I/O files are redo log files, then consider splitting the redo log files from the other files. Possible configurations can include the following:
Redo log files are written sequentially by the Log Writer (LGWR) process. This operation can be made faster if there is no concurrent activity on the same disk. Dedicating a separate disk to redo log files usually ensures that LGWR runs smoothly with no further tuning necessary. If your system supports asynchronous I/O but this feature is not currently configured, then test to see if using this feature is beneficial. Performance bottlenecks related to LGWR are rare.
http://docs.oracle.com/cd/B19306_01/server.102/b14211/iodesign.htm
JonK1
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August 16th, 2012 07:00
Yeah, but I'm then also wondering whether redo logfiles should actually be put on RAID5 instead of RAID10. Remember that full stripe writes on RAID5 are cheaper than writes on RAID10. So there the move to RAID5 would actually improve back-end load!?