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SP A and B Balance

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Currently I have 6 shelves of FC drives (72GB and 300GB) and just added a shelf of 15 SATA II 1 TB Drives.

I am setting up two RAID 5 Groups 6+1 with a hot spare.

Currently there is no rhyme or reason as to which LUN's are associated to SP A or B. My question is would you assign the first RAID Group to SP A and the second to SP B? Like I said there does not appear to be any rhyme or reason as to how they were assigned before.

Best practices appear to say balance load across both SP's but does not really clarify if my putting all of the first set on A to be an issue or not.

Thanks!
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Re: SP A and B Balance

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What I am trying to understand is...would there be an issue if I assigned all the LUN's from one RAID Group to SP A and all the LUN's from another RAID Group to SP B?


No. In many cases users find it easier to provision this way. The LUN Provisioning section in Glen's suggested reading: EMC CLARiiON Best Practices for Performance and Availability, FLARE Revision 28.8 contains a lengthy discussion on LUN provisioning and balancing.

Balancing the load across RAID groups, back-end buses, and Storage Processors is an important concept with the CLARiiON. It is how you get the highest utilization and best performance out of the storage system. You can find a higher-level discussion of these resources and how to balance across them in the EMC CLARiiON Storage System Fundamentals for Performance and Availability. Both these documents are available on PowerLink.
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Re: SP A and B Balance

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You assign a LUN to an SP, not the Raid Group. You decide which LUNs are owned by which SP. This is determined by the workload that each server will be generating. You can use Navisphere Analyzer to collect performance data (see the Navisphere HELP about using Analyzer) - this date can show you where you load is - either SPA or SPB. Then you can determine which LUNs are generating the load.

You might want to review these documents - I've included both FLARE 26 and FLARE 28 as I'm not sure what type of array you're using.

White Paper: EMC CLARiiON Best Practices for Navisphere Performance in Large Configurations ¿ Best Practices Planning

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h6099-navisphere-performance-...


EMC CLARiiON Storage System Fundamentals for Performance and Availability

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/H1049_emc_clariion_fibre_chan...


EMC CLARiiON Best Practices for Fibre Channel Storage: FLARE Release 26 Firmware Update - Best Practices Planning

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/H2358_clariion_best_prac_fibr...


EMC CLARiiON Performance and Availability Release 28.5 Firmware Update Applied Best Practices.pdf

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h5773-clariion-perf-availabil...

glen
8 Krypton

Re: SP A and B Balance

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Sorry if I did not pose that question clearly. I understand that I do not assign the SP's to a RAID Group. What I am trying to understand is...would there be an issue if I assigned all the LUN's from one RAID Group to SP A and all the LUN's from another RAID Group to SP B? Since currently we do not have any type of pattern across the SP's.
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8 Krypton

Re: SP A and B Balance

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What I am trying to understand is...would there be an issue if I assigned all the LUN's from one RAID Group to SP A and all the LUN's from another RAID Group to SP B?


No. In many cases users find it easier to provision this way. The LUN Provisioning section in Glen's suggested reading: EMC CLARiiON Best Practices for Performance and Availability, FLARE Revision 28.8 contains a lengthy discussion on LUN provisioning and balancing.

Balancing the load across RAID groups, back-end buses, and Storage Processors is an important concept with the CLARiiON. It is how you get the highest utilization and best performance out of the storage system. You can find a higher-level discussion of these resources and how to balance across them in the EMC CLARiiON Storage System Fundamentals for Performance and Availability. Both these documents are available on PowerLink.
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8 Krypton

Re: SP A and B Balance

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Thank you for your answer!
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Re: SP A and B Balance

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Can anyone tell me if you can change the SP from A to B or B to A after you have presented them through PowerPath? The reason why I ask is if down the road I have a heavier load on A than B I would like to be able to change the ownership to balance it out. Thank you!

PS...since the main question was answered...should I start a new thread or is it ok to repost to this as I did...just want to make sure :-)
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8 Krypton

Re: SP A and B Balance

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Yes, you change the SP ownership of a LUN at anytime. When you attach a host to the array you should have redundant paths to each SP, so changing LUN ownership should be non-disruptive to a host.

First change the SP owner properties of the LUN, then trespass the LUN to the proper SP. You will find this is a common process when managing a CLARiiON array. When deploying LUNs you may not know what the exact performance characteristics of the application will be and may find that the SPs are unbalanced after analyzing the array over a period of time. So it is common to rebalance LUNs to achieve optimal load on the array.

Don't worry about starting a new thread, it is your thread and you are on topic still IMHO. The moderators here aren't strict about stuff like that.
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8 Krypton

Re: SP A and B Balance

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Great, thank you so much for the information this helps a lot! I appreciate it!
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