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FR-096_f

3 Posts

2286

March 14th, 2007 11:00

Basic Best practise and Reporting question from a newbie!

We have a CX500 with mixture of FC and ATA disk trays. Is there a best practise in how the SP's should be allocated among the LUNS/trays.

ie. Should the SP A be for FC based LUNS and SP B for ATA LUNS, or does it not matter as far as LUNS are distributed evenly among the the SPs?

Another question I have is, is there a Reporting tool that I can use to analysis LUN/Raid group usage in the same fashion as on does on Windows servers using Perfmon?

I have used SAN Analyser, which is good for real time, but can I log it somewhere and analysis it later?

Sorry if these had been answered before.
Thanks in advance

an_hidden_KB

87 Posts

March 23rd, 2007 03:00

configuring RLP on ATA would result bad performance problems in most environments. for details please see the whitepaper: EMC CLARiiON Reserved LUN Pool Configuration Considerations - Best Practices Planning

Allen Ward

6 Operator

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2.1K Posts

March 23rd, 2007 09:00

It does depend a lot on what you are using the RLP for . In our environment we have a CX3-80 and a CX700 running SRDF/A. On the source array we use FC drives for the RLP (to maintain performance). On the target (DR Site) array we use ATA because the performance doesn't matter. This saves us a fair bit at the target end and does not impact production performance at all.

But it is true that in MOST situations this wouldn't be the best config.

dynamox

11 Legend

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20.4K Posts

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87.4K Points

March 27th, 2007 05:00

Allen,

something got me curious about your post ...did you mean Mirror View when you mentioned SRDF/A ? I thought SRDF/A only runs on Symmetrix ?

Allen Ward

6 Operator

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2.1K Posts

March 27th, 2007 06:00

Sorry about that, and thanks for pointing it out. We are indeed running MirrorView/A between those two arrays.

I'm in the midst of a conversion from a pair of Symm 8830 arrays running SRDF Adaptive Copy migrating to a pair of DMX3s running SRDF/A and I apparently have that stuck in my brain.

EKellerman

76 Posts

March 27th, 2007 06:00

Hmmm....Good catch, thats what I thought too. ?:|

tim0871

15 Posts

March 30th, 2007 06:00

I can attest to the "don't use ATA for reserved LUN pools" comment. We put in a new CX500 when they were first released and the BP at that time was to use ATA for this purpose. We had local clones and quickly ran into a problem when a forced cache flush event took place. The ATA's couldn't perform the writes at the same rate as the FC, so the whole flush had to wait on the ATA's. In the mean time, no more I/O was being allowed to take place, causing queue lengths to stack up. Once this happened, it was nearly impossible to get back to a normal status. We had to kill all of our clones and snaps.

I woudl still question the use of ATA for your DR copy with Mirrorview/A. I assume that you have the data there so that if you needed to operate from that SAN you could. Would those drives be able to really handle your load when you needed it? It may be a cheaper way to implement the DR, but will it support your needs when you need it most?

Allen Ward

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2.1K Posts

March 30th, 2007 10:00

Maybe I didn't describe the use of the drives in DR as well as I should have.

At the DR site the ATA drives are used for the RLP to minimize the cost of having lots of RLP space available. The RLP is ONLY used for MirrorView/A at the DR site so if we failed over and ran prod from DR the data would actually be running off FC drives and the ATA drives would be unused (until we got our primary site back up again).

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