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I have a Hyper-V server w/ 2x500GB drives on RAID1. I would like to replace these with 4x1TB drives on RAID6. I have four VMs on one host, and can get by with just restoring the VMs on a new host installation.

I'm trying to figure out the best (safest) way to do this but also minimize downtime. I'm afraid my options are limited, and will result in more downtime than I can afford.

Here is what I'm thinking, but wondering if others have a better strategy:

  1. Copy off VMs to another server.
  2. Swap 2x500GB HDDs w/ 4x1TB HDDs.
  3. Set up RAID and install clean Hyper-V host.
  4. Copy over VMs to new host & set up.

Assuming this is the best approach, I'm still probably looking at a few hours downtime at best. So just wondering if there's a way I'm not thinking of I could do this with less downtime.

Unfortunately, this is a single-server environment, but I do have another server I can use just to store the VMs during the migration.

Update: Some updates regarding specs. This is a Windows Server 2012 Hyper-V host w/ 2x Server 2012 VMs, and 2 Server 2012 R2 VMs.

The server is a 1U Dell Poweredge R310, with 4 HDD bays, and hardware software RAID, Dell PERC S100 controller.

I'm not set on 1TB drives, or HDD vs. SSD, and can afford to spend a little more if it makes sense. But I do need more capacity, would like more redundancy, and would like to keep performance at least on par with or better than RAID1.

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  • What are you using to create the RAID? Are you on a hardware controller (what model?) are you using software RAID? Storage Spaces? How many drive bays are available?
    – MDMarra
    Oct 7, 2013 at 15:32
  • What OS is installed on the host? Also, don't copy the VM's, export and import them. If you're running Windows Server 2012 and you have another host available you can perform a "shared nothing" migration of the VM's, which will help to reduce your downtime window, allowing you to run the VM's while you rebuild the original host.
    – joeqwerty
    Oct 7, 2013 at 15:40
  • @MDMarra 4 drive bays on this server (Poweredge R310). I don't know the RAID controller model, but it is definitely hardware RAID.
    – Jerad Rose
    Oct 7, 2013 at 17:15
  • @joeqwerty I'm on Windows Server Hyper-V 2012, and the VMs are Server 2012 (2) and Server 2012 R2 (2).
    – Jerad Rose
    Oct 7, 2013 at 17:16
  • @MDMarra Added RAID controller. It's a PERC S100 controller. Looking deeper, this may be a software-RAID controller (thought all controllers were hardware RAID?).
    – Jerad Rose
    Oct 7, 2013 at 17:34

2 Answers 2

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Don't use RAID6. Use RAID10. With 4 drives you get the same level of protection but better performance.

Depending on your controller, you can do this migration with no downtime. For example, with an HP SmartArray, I would swap each of the 500 GB drives for 1 TB drives, allowing for re-mirror between. Then insert the 2 additional 1 TB drives. Then use the Array Configuration Utility to add the 2 new drives to the array, and finally reconfigure the array to grow the volume and switch to RAID10. No downtime needed!

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  • Thanks. So I checked and have a software Dell PERC S100 RAID controller. Looks like it supports hot swapping, so theoretically, I could 1) Swap drive 1 (500GB) with new 1TB drive, 2) let it re-mirror, 3) swap drive 1 (500GB) with second 1TB drive, 4) let it re-mirror, 5) add remaining two 1TB drives, 6) grow the volume and change to RAID10. Does that sound right?
    – Jerad Rose
    Oct 7, 2013 at 17:49
  • Also, a bit unrelated, but should I take this opportunity to replace the older software RAID controller w/ a hardware RAID controller?
    – Jerad Rose
    Oct 7, 2013 at 18:05
  • A hardware controller does everything in hardware. A software controller is usually a feature of the operating system. A host based controller is a fairly standard disk adapter but it runs specialized software that performs the raid operations using the computer's processor. This is also called fake raid. The s100 is a fake raid controller. If you can install a hardware controller that would be a good idea since you are using such large drives. Note that you might not be able to just swap the controllers without erasing the disks so make sure you have a backup.
    – longneck
    Oct 7, 2013 at 20:53
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I spoke with a Dell technician about my setup and what I wanted to achieve. Turns out, it's not so easy going from two-disk RAID1 array to RAID6 or RAID10. According to the tech, I would have to blow away my existing array and rebuild it from scratch -- basically what I had in the OP.

We did discuss another option though, and that was dual RAID1 arrays, just to buy me some extra storage without having to rebuild. While that's not what I was going after originally, it's probably what I'll drop back to for now.

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  • 1) install hardware raid controller, connect to just 2 drive bays. 2) insert 2 new drives. establish mirror. 3) in windows drive management, make this new raid volume a mirror of your existing s100 array. 4) when mirroring is complete, power off the server and remove the s100 drive. 5) power on to make sure it works. 6) power off and connect all drive bays. 7) add additional drives and reconfigure array to RAID10. (this could be done in many different ways, including using a linux USB drive to copy from the old to new array.)
    – longneck
    Oct 8, 2013 at 2:45

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