SATA vs SAS vs SSD for Virtual Machine Automation

hyper-vscvmmstoragevirtual-machines

We're using SCVMM and Hyper-V hosts to manage our Automated VM environments. Currently we have two servers with 3 7.2k consumer drives each (one for host OS/Storage, two for VMs). It's hard to say if it's the quality of the drives, but right now we can't get more than two VMs to run concurrently on each drive without it interfering with automated UI testing. I say it's the drives because we have excess memory availability and low CPU usage.

I was looking into some input as to the benefits of SAS vs SSD vs SATA drives for a situation such as this, since we're adding a third server and it's a good time to rework our storage system. The actual automation has fairly low IO demand but since we're attempting to run as many machines per drive as possible, I'm not sure what to go with.

Research has not been terribly helpful as most articles and forum posts regarding this subject revolve around home server use or virtualized server/database use.

Best Answer

It's a balance between price and performance.

Mechanical SATA drives obviously have better prices but are in no way designed for such jobs, so for a serious business it's a no-go

SAS protocol has enhanced features (for example queue re-ordering) that allow them to better manage I/O from multiple VMs and so they are much-more efficient (even with the same mechanical parts) than mechanical SATA for this usage.

SSD have good write performance and very good read performance, but are available in smaller size, or at equal capacity, are much more expensive.

SSD are also (like mechanical drives) divided into consumer-grade and enterprise-grade. The second having, for example, more spare cells to replace used cells, more buffers, better trim management.

Also, most of SSD use a SATA interface but now you will find SSD with SAS interface, making them the top choice regarding pure performance.

So the choice is really about needed capacity / price / performance, but you should select enterprise-grade product, especially if you intend to use RAID.

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