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6 Drive RAID Configuration for VM Server

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December 13, 2011 3:39:13 PM

I’m new to virtualization and I’m setting up two new servers. My question is what’s the optimal hard drive configuration? I have an LSI MegaRAID SAS 9265-8i but my servers are limited to only 6 drives. With only 6 drives I’m unable to do a RAID 10 across all drives so here are my options:
1. RAID 10 on 4 drives and booting off the other two drives in RAID 1
2. RAID 5 on all 6 Drives
3. RAID 50 on all 6 Drives
Any assistance is appreciated.
December 14, 2011 7:17:13 AM

You should be able to RAID10 6 drives. You need an even number, which you have.

As for which is optimal, it depends what you're doing with the servers. For a database load where you have many random accesses and you need maximum iops, RAID10. For a file server where you have sequential accesses and need storage space, it will depend on the load. RAID5 might be a good option then.
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December 14, 2011 7:48:13 PM

If you're heading into VM territory, it helps to centralize your storage on a SAN, typically one connected via iSCSI or Fibre Channel.

The advantage to a VM environment is that your servers can simply act as hosts which handle processing and RAM. If one fails, your VM's can automatically move to the other because they're actually stored on the SAN.

If you plan on using each physical server to host multiple virtual servers, with no centralize storage, you're risking one piece of hardware taking down MULTIPLE servers. Not a good idea.

In any case, if you go through with this design and plan to keep each host in its only world without redundancy, then I suggest a simple RAID5 with a hot swap drive. RAID 5 is a solid choice for both reads and writes and it will also give you more usable storage than RAID 10.

If you're aiming to store a database on the RAID, then you'll want RAID 10 for the database, but if your logs are writing to the same LUN, then it completely defeats the purpose of using RAID 10. The optimal configuration for a database would be a RAID 10 for the database and then a completely separate RAID 10 for your logs. With only 6 drives, this really wouldn't work. You don't really have enough spindles for good performance with a database.

But then again, it also depends on the database size and the amount of transactions. Lots of variables here. Hope this helps.
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