VmWare RAID Configuration

Looking for some suggestions on how to setup my storage array for vmware usage.  Here is my setup:

(2) Proliant GL 380 G6 (Dual E5540 2.53 Ghz, 36 GB Ram, 2x300 GB SAS, (4 CPUS, 76 GB RAM Total))
(1) HP StorageWorks MSA2000 with (12) 450 GB SAS 15k

We are a school system of about 500 users, 1400 Pcs, 20 servers.  

I have a software vendor that is using SQL Server who is requiring 3 separate RAID 1 storage arrays (1 for logs, storage, and temp files).  Of course this burns up 6 of my drives and wastes a lot of my space for vms.  I also have Exchange to setup on a VM as well.

My Question is should I follow their recommendation and what if any is the performance hit.  Some options:

(3) Raid 1 450 GB Arrays ( 6 drives used) for SQL
(1) Raid 5 2.2 TB Array (6 drives used) for vms

OR setup (1) large Raid 50 Array with several different volumes on it (for vms and sql).  The vendor says that I will get more I/O  by having the separate arrays... but i do not understand that as you get no performance increase from a Raid 1 configuration.

Or a hybrid of the 2.  I want to get the most out of the StorageWorks for SQL and Exchange without giving up all the space and leaving me with no room for VMs.

Any questions/comments appreciated... i have seen several similar best practices questions on experts exchange already, but none seemed to quite fit my situation.  In summary the question is if it is better to have independent arrays with Raid 1 or to have a hybrid Raid solution with striping that improves performance for vms, sql, and exchange?

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"tahlequahitguys", that SQL vendor is assanine! I mean, are you for real???...3 RAID1s solely for themselves????? That is not at all SQL best practices. If anything, there should at least be a RAID5, then RAID1 for logs, etc. Is this RAID they are requiring unavavoidable?

My recommendation is to create 3 RAID5s (if you don't *have* to have 3 RAID1s for SQL vendor). From this you can place most of your VMs on 1 RAID5, then have your SQL DB on part of the 2nd RAID5, and your Exchg SGs on the 3rd RAID5 (I recommend using RDMs for your SQL DB & Log storage as well as your Exchg SGs). You can disperse low I/O VMs on the 2 RAID5s that house RDM LUNs for SQL & Exchg.

So, to answer your question, no it is not 'best' to have 3 RAID1s and then a RAID5...you lose too much storage, and you really don't have good performance with RAID1 as it's just a mirror; RAID5 on the other hand is designed for performance (and of course failure recovery).

Hope that helps.

tahlequahitguysAuthor Commented:
Yes... yes i agree....  really what i am trying to avoid is the "i told you it would not work" from the vendor or somehow blaming our configuration on why the program performs poorly.  i think ultimately they will have to live with whatever we tell them to do.

They will install it remotely and will never actually see the server, so they will not know the configuration on the back end.  As long as it performs, i do not really care.

Just another FYI.  The msa2000 is accessed through a 4 port 1 GB iSCSI.
OK, then you should be good to go. Not sure if you've seen it, but here is VMware's iSCSI SAN Config Guide. It has obviously config steps, as well as best practices, that are worth looking at.

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For 20 servers.....I would maybe use Raid10 12 x 450GB giving you a high performance  2.7TB array. On which you can then create your SQL LUN(s) and VMFS LUN(s) as needed. Raid10 offers better seq/random writes than Raid5. Although Seq/random Reads is about the same as Raid5.

I would also perhaps consider using 2 spare and make it a 2.25tb array instead but it would cost 2 spindles performances wise.


VMware has a 2TB limit (although you can create an extent), so I wouldn't go with a 2.7TB (or 2.25TB)  array...I'd split it up. RAID10 does have better performance at the hardware level, but from an end user (or Sys Admin) standpoint it's not really noticeable (not in my experience). Just my extra 2¢ worth. :)

andyalderSaggar maker's framemakerCommented:
I'd stick to a single RAID 10 for performance unless you need the space and then slice it into two LUNs because of the 2TB limit coolsport mentions, but that is contrary to Microsoft's recommendation that transaction logs and data should be on separate spindles so that no loss recovery can be performed if one set of spindles completely fails. To stick with MS recommendations you would have to split into two RAID 10s of 6 disks each instead, then spread the load by for example having Exchange data and SQL logs on one set of disks.

The SQL vendor is going by MS best practices though, separate sets of spindles for data, tempdb and logs (and OS) but it really isn't viable because Exchange best practices also stipulate separate spindles for data, logs and OS, and that makes a minimum requirement of 14 disks just for those two VMs.
tahlequahitguysAuthor Commented:
irritating... i guess i need another NAS lol... now i am curious.  i guess i dont know enough about the IO process.  Does having inidvidual arrays actually increase IO versus having a big RAID 10 or 50?  i guess i understand how that works because the work is being done on the dedicated array by 1 server vs all the drives being accessed by multiple servers.  i guess the question is how much?

so... performance wise... it would not make a huge difference between 3 separate arrays vs a raid 10 with 3 luns?

Thanks all for your input... i will award points soon before the end of the day.
andyalderSaggar maker's framemakerCommented:
One big array with everything sharing is normally optimal if you ignore the MS recommendations, after all if one application is not busy other apps benefit from the extra spindles. You wouldn't have to buy another MSA2000 if you wanted more disks, they have expansion enclosures available.
Well "tahlequahitguys", you really don't want to have a single RAID (IMHO), whether it's a 5 or 10, because doing so opens you up to a single point of failure, disk-wise. Sure, you can lose multiple disks in the array, but I just don't trust having 1 single array. Also, I think it's best to separate your DBs...your SQL DB and Exchg DB. I think separating your DBs on different arrays will give you better performance than having it on a single RAID10+. And again, I really don't think you're going to notice a big performance difference otherwise. Now, in saying that, you may want to stick to at least some best practices, but in assuming the size of your org/configuration, having RAID5s will work just fine, plus you have decent performance, and decent failure recovery.

It's always a fine line in discerning how best to configure storage in a virtual infrastructure. Sometimes it just boils down to what you're best comfortable with in implementing, while still meeting your SLA requirements. :)


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tahlequahitguysAuthor Commented:
It seems like there is a lot of grey area in setting these kinds of things up.  I think i am going to do a hybrid approach.  maybe 2 raid 1s for sql and place the rest in 2 raid 5s or 1 raid 50... still thinking :)

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