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New raid groups or Expand exisiting one
Hello all,
We are planning to expand a CX4 -240 array.
Any one can advise whether to expand the existing raid groups or just create new one ? what are the pros & cons for both ?
thanks
kenn2347
542 Posts
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December 6th, 2011 07:00
Can you give us some more info on your expansion? How many shelfs are you adding? Are your current Raid groups full? Are you using Pools?
Expanding a raid group can take a long time depending on the disk type and size.
Also, what FLARE are you running?
Joe_Ab
227 Posts
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December 6th, 2011 08:00
10 RG , 5 of them are almost full . will add more 5 shelfs. no pools are yet created. using flare 4.30 , thnx
kenn2347
542 Posts
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December 6th, 2011 08:00
Looks like you are adding a good amount of disks. The question will be is there a benefit of expanding the existing RG's. If you have data that needs a lot of IOPS you might want to expand an existing RG to get the benefit of the extra spindles. Just keep in mind that there are RG limits as to the number of disks(16) and that it could be a long process. During the expansion, you will take a performance hit on that RG till it is finished
I would not expand a RG just to get more space to create more LUN. you might run into an issue where you have to many things on a single LUN. If all you need is space, i would create new RG's with your new disks. This is also a chance to create a new Thinpool with all your new disks. I am not sure if they have changed it but before if you had a thin pool and wanted to add more disks to it, it would not restripe the data across the new disks. SO plan you thin pool correctly now. I think the optima configuration is to create the thin pool with groups of 5 disks.
hope this helps
kelleg
4.5K Posts
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December 7th, 2011 13:00
If you're thinking about Pool (with flare 30, Pools are now renamed to Fast VP Pools - they can have both Thick and Thin LUNs), you should take a look at the White Papers for Pools first as Kenn suggested. Pools if done correcctly can be very useful, but if you try to create one large Pool, you may see issues with performance.
Here's a couple of very good documents about using the CLARiiON for best performance:
EMC CLARiiON Performance and Availability Release 30 Firmware Update Applied Best Practices.pdf
http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h5773-clariion-best-practices-performance-availability-wp.pdf
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_channel_storage_fundamentals_ldv.pdf
For information on Pools see the below:
White Paper: EMC FAST VP for Unified Storage Systems — A Detailed Review
http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h8058-fast-vp-unified-storage-wp.pdf
For best performance consider metaLUNs:
White Paper: An Introduction to EMC CLARiiON Storage Device Technology — Applied Technology
http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/H4208-an-intro-emc-clariion-hard0drive-tech-wp.pdf
Glen
Joe_Ab
227 Posts
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December 7th, 2011 22:00
great answers glen and kenn. Thank you.