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Software Raid vs Hardware Raid for Openfiler

Last response: in Storage
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March 15, 2011 8:44:00 AM

Hi,

I have a box with AMD Phenom X4 as the processor. I got 4 Hard Disks. I am thinking of 2 options:

Option 1
Installing Openfiler in the Box
Software Raid the 4 Hard Disks


Option 2
Installing a Raid Card, lsi megaraid 9260-8i
Perform a Hardware Raid on the 4 Drives
Installing Openfiler in the Box


I will like to use this box like a SAN, i.e. allocating my VMs LUN to run on. I was reading an article like:

http://www.zdnet.com/blog/storage/can-software-raid-be-faster-than-hardware-raid/126

that claims that Software Raid can be faster than Hardware Raid. Is that really true? In that case... I might be able to save on a LSI Raid Card.
March 15, 2011 8:16:57 PM

Software RAID should work fine. It all depends on how many VMs you will be running and how IO intensive they will be.

The article you pointed to is four years old, and was using ZFS instead of OpenFiler but for a few VMs it should be fine. Keep in mind the statistics they pointed to were using an EMC Clarion array with 40 disks. You are using 4, so your thoughput will be much lower. They also don't quote IOPs in the article, or the exact test scenarios. Dedicated storage processors (such as those on an LSI card) are good at prioritizing and queuing requests, which leads to higher IOPs. IOPs tend to be much more important then throughput.

Throughput will be a concern, though, since I am guessing you will be using GigE and your server as an iSCSI target. GigE is much more limited then a dedicated bus (PCIe) for storage throughput. Again, in small scenario this shouldn't be an issue.

I would go with the software option, unless you are using the VMs for storage intensive applications (or more then 10 active VMs).

Matt
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