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victory_is_mine
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236 Posts
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April 4th, 2015 08:00
Preferred disk count in VNX private RAID groups
Hi All,
I was looking for some kind of explanation as to why 6+2 or 14+2 is the preferred disk count for RAID6 pool? Or why 4+1 or 8+1 is the preferred disk count for RAID5? It does not mean though that I cannot use 4+2 for RAID6, or 6+1 for RAID5. Does anyone know how to explain this? Why EMC has this preferred disk counts, and what is going to happen if I use nonpreferred disk counts in my VNX configuragtions?
Appreciate your input.
victory_is_mine
2 Intern
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236 Posts
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Posted April 8th, 2015 10:00
I did. It still does not provide a good explanation of why this particular drive count is preferred, unless I am not seeing something.
Joshua_Fawcett
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Posted April 29th, 2015 10:00
Ad_Astra,
The short answer would be that that is what EMC has found to be the best size for the RAID group for the most I/O workloads and applications. Ultimately the goal is to achieve full stripe writes to your disks and these sizes seem to bring in the greatest amount of full stripe writes.
I've attached a document to my post. It's another best practice guide. If you skip straight to page 77 if discusses the RAID level performance characteristics and discusses the preferred RG sizes. I'd recommend starting a little higher on Page 74 and reading for a few pages to get some great background information on RAID leading up to the performance characteristics.
Hope this helps.
1 Attachment
VNX Performance Best Practice Guide.pdf
VNX Performance Best Practice Guide.pdf
Jyothi_P_Bharat
317 Posts
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Posted April 6th, 2015 00:00
Hi,
Please check the below mentioned link:
http://www.storagenetworks.com/documents/emc/emc-vnx-best-practices-wp.pdf
(from page num13)
Thanks
Jyothi