Recommended HDD/RAID Configuration for Hyper-V Server

Question

_{Saturday, October 20, 2018 2:58 AM}

I have read over articles about best practices in setting up Hyper-V server.  What I read seemed to indicate putting the page file on a separate disk than the operating system and similar with the virtual machines was a best/recommended practice.  Is this recommendation geared around putting them on separate physical disks or separate partitions?

I have a Dell R710 server that I'm building a small home lab on and will run a several virtual machines, most likely under 10.  The server came with four 300 gb 10k rpm 6gb/s SAS drives.  I have four more bays and was looking at one of the three scenarios

1. Getting four more 300 gb drives
2. Getting four 600 gb drives of the same speed/rpm to add to the server
3. Or getting eight 600 gb drives and replace the four 300 gb drives (sell them on eBay or something)

Obviously adding four more 300 gb drives is the cheapest option, but not sure if it will give me all the drive space I'll need for the future.  If I went this route, what would be the best RAID configuration?  Do I setup a RAID 5 or 1 setup for the OS and then create a large RAID 5 or 10 array for the virtual machines?  My thoughts on the 300 gb drives is that going with a RAID 5 setup it may be wasting space on the OS array/partition if I just have the Hyper-V host OS.

If I add four 600 gb drives I should have plenty of space for the virtual machines, but again am I best utilizing the 300 gb drives for space and configurability?

If I add eight 600 gb drives, again what's the best configuration?  Is a RAID 10 setup as one large array or setting up a smaller array and larger arrary?

Thank you in advance for any comments or feedback on a recommended setup or links to something to read.

Josh

All replies (3)

_{Saturday, October 20, 2018 4:58 AM ✅Answered}

There aren't any universally applicable "best practices" in this space and most of the articles that I've read on the subject contain mountains of demonstrably incorrect information.

Some pointers:

• Hyper-V and its management operating system will use almost no I/O if used properly (as in, don't go installing a bunch of stuff). The hypervisor will never use the page file under any circumstances. The management operating system should rarely use it. Separating the management operating system's page file onto another disk is a complete waste of time, space, and effort. There is some anecdotal evidence that manually specifying its size might help with things like patching. It does not need to be a large page file, though.
• The only justification for separating a guest operating system's operating system from its page file is if you intend to enable replication over an inter-site link. In nearly any other configuration, it is a waste of time, space, and effort.
• The "best" RAID is a matter of perspective and need. RAID-10 generally gives the best performance but at a substantial capacity cost. RAID-5 balances performance and space utilization. RAID-6 gives relatively poor performance but provides a higher level of protection than RAID-5 and more capacity at 5+ spindles than RAID-10. I have read a lot of FUD around the premature death of RAID-5 but it's all smoke and mirrors.
• Spindle count in an array of spinning disks determines the performance of the array more than any other factor.

I tend toward one large array because Hyper-V and the management OS are relatively small and need so few IOPS that dedicating spindles for them is a crime. My RAID choice depends on the project's desired position on the scale between greatest performance per dollar and greatest space per dollar. In your case, I would employ RAID-5 on one big array because you mentioned capacity as your concern. If you stay with 300GB disks, that will give you roughly 2TB formattable space which should be plenty for most anything short of a media server.

Eric Siron
Altaro Hyper-V Blog
I am an independent contributor, not an Altaro employee. I accept all responsibility for the content of my posts. You accept all responsibility for any actions that you take based on the content of my posts.

_{Sunday, October 21, 2018 3:05 AM}

Eric,

Thank you very much for the reply and information!  Everything you mentioned makes sense vs. some of the "best practices" documents I've read.  I will plan to go for one big RAID 5 array and keep the page files with the OS partition.

Thank you again for the information!

Josh

_{Wednesday, November 7, 2018 6:41 AM}

Hi,

Thanks for your updating.

If there is any question, please feel free to let me know.

Best Regards,

Frank

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