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I recently purchased a SansDigital external RAID enclosure for my WHS. I have 4 drives I was going to use in it. Should I use the disks individually and let WHS handle the duplication or should I use the software RAID to do RAID 10 or RAID 5?


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closed as off topic by Bryan, MDMarra, Ward, mdpc, Dennis Kaarsemaker Jun 8 '13 at 15:42

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up vote 6 down vote accepted

Wait! Wait!

The question about what the best RAID level is for a generic server at home, and whether/what RAID to use for Windows Home Server are two very different questions.

Windows Home Server uses a special technology called Drive Extender that works in the background to ensure that data is always on two physical drives. If any given drive dies, you can replace the drive and your data will be replicated back to the new drive. All of the benefits of RAID with none of the hassles.

However, in order to work it's magic, Drive Extender works at a very low level (specifically, it uses a file system mini-filter driver in addition to the NTFS file system to implement Shared Folders storage technology). From KB 946676 "File system mini-filter drivers are an extensibility mechanism that is provided by Windows to enable storage scenarios. For distributing data across the different hard drives that are managed by Windows Home Server, the Windows Home Server mini-filter driver redirects I/O between files that are stored on the main hard drive and files that are stored on other hard drives". All well and good, but when you have two low-level file technologies (the Drive Extender mini-filter driver and the RAID software) working low-level magic to make multiple drives appear as one, duplicate data, and place it on multiple drives, you run a STRONG risk of having something go wrong.

If you want to be sure that your data is safe in the event of a drive failure, use the technology built into Windows Home Server to do this. Your backed-up data will always be on at least three physical disks (your main computer and two physical disks in the Windows home Server). Also better than RAID is the fact that you can add any hard drive any time and it will be added to the pool. No worries about matching drive sizes for your RAID volumes, drive letters, LUNs, etc). You can add internal or external drives and they all join the same pool. If you want to remove any of the drives, again no problem (it would be with several of the RAID levels mentioned above).

All right... I'll get off my soapbox. :)

If you want to read the white paper on how the technology works behind the scenes, you can do so here: Technical Brief: Windows Home Server Drive Extender

From the white paper:

It is highly recommended that you not use hardware RAID technologies for your home server. Recovering from hard-drive failures becomes increasingly complex when hardware RAID systems are used. The recommended and supported approach is to use multiple hard drives that are configured as Just a Bunch of Disks (JBOD).

I wanted to know if WHS would work better with this disk in RAID or using WHS duplication. Great answer – Steve Wright May 28 '09 at 1:26

This is a home server. I think that RAID 5 is quite sufficent.

The long and the short of it is that the lower you can implement the redundancy the better. If the device uses a hardware level RAID, go with that. Even if the device offers a software level, it is bound to be optimized for the hardware. I would suggest that you use the Windows OS to implement RAID5 or mirroring only as a last resort. It is easier to manage from the OS GUI, but there can be a performance hit.

That being said, it IS a home server, so there will always be some trade-offs between "safe" and "cost effective".


I wouldn't recommend RAID5 for data that you really want protected. RAID 6 would at least guarantee that you could lose 2 disks, but you lose half of your storage space. With RAID 10, you have a 25% chance of data loss with 2 drives dying.

I vote software RAID 6.

For a home server, RAID 5 and a good backup regime should be more than enough. – Sam May 27 '09 at 22:35

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