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matteo nunziati
Asked: 2017-01-28 08:27:31 +0800 CST

storage for virtualization: 10x15k sas w/ 2gb cache OR 10x10k sas w/ 4gb cache

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sorry for the long title.

this is the point: due to a number of decisions it doesn't worth to share here and which do not completely belong to me, I'm facing the choice of 2 different storage solutions for a virtualization server:

  1. use a SAS-attached SAN with 10 SAS disks at 10k rpm (12gbs). Those disks will be set in raid under a controller with 4 gb cache (6gb, 2 of which for SAN OS and for metadata, 4gb for actual data).

  2. use local disks on the server: same amount of disks but at 15k rpm, the raid controller having "only" 2 gb of cache.

everything else in the config (number of sockets, type of processors, amount of ram, type of raid... which is raid 6) will be the same.

honestly I can not estimate which solution would be faster considering that the storage will be used for virtualization of a number of workloads:

  • ERP with documental storage, DB (Postgres) and mail accounts (IMAP)
  • WMS with SQL express db
  • other db "intensive" apps

expected concurrent users will vary between 30 and 50 constantly checking emails and adding data entries in the ERP as per customer orders received by the company.

I don't really know how much useful the cache would be in this scenario, and if the additional 2gb of the SAN would be on par with the additional IOPS/throughput provided by 15k rpm disks.

for what concern the SAN, being a SAS attached SAN it is to me more of a DAS, with the possibility, in future, to add a second server attached to it for HA (vMotion and similar stuff).

I do not expect the SAS attached storage to perform differently from the local disks performance wise, I mean: no fiber channel of any kind of networking between SAN and server. am I wrong?

I expect the performace to be related to disks rpm and - maybe- cache. But don't understand which mix would be faster.

any suggestion? Clarifications? Missing points?

Thank you!

virtualization performance storage

1 Answers

  1. Best Answer

    From my experience, it would be better to take into consideration SSD instead of 15K SAS drives. Right now with such technology growth speed, SSD's are making cheaper and cheaper, so the difference in cost is miserable. Also, you can take 10K SAS drives and few SSD's to create tiered storage with built-in Storage Spaces functionality. You can share this drive over iSCSI with Starwind free, but I don't remember does it working with Storage Spaces, I guess their engineers can answer this question. Hope it helps. https://www.starwindsoftware.com/starwind-virtual-san-free

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