Windows Home Server, redefining the idea of RAID

May 16, 2009

Windows Home Server is a sort-of offshoot of Windows Server 2003 designed for home users. Yes, home users. But don’t let that give you the impression that this is a Disneyland vacation… Home Server has effectively “created” technologies that will easily revolutionize the entire IT industry, if Microsoft allows it to.

Drive Extender is at the heart of it all. Drive Extender is a sort of “file based RAID”. Unlike RAID, where the drives are merged and mirrored at the physical level, Drive Extender’s RAID works with files at the logical level. It puts all the files in one “place” using a “landing zone” (primary) drive that has links to all the files on the other drives. It places the actual file on another hard drive (volume) in the array, then creates a hardlink in the “landing zone” drive. So when you browse to the main drive, or the network share, you see all your files there, although the files in the folder may be stored on 5 different hard drives.

Oh, man, the implications this has… and they’re all good. First, imagine you were on a LAN and 100, maybe 1,000 people were accessing files on that share. With a standard RAID array, parts of each file are stored on all the drives – so… all the drive heads move in unison and there is no random-access benefit. Accessing more than one file simultaneously slows the system to a crawl. Well, with a Drive Extender RAID, all the files are stored on different drives. So there’s an excellent probability that the two files the people are accessing are located on different volumes, and there is no bottleneck at all as each drive reads the requested file.

Screenshot of Home Server's storage console, showing drives in the pool

Screenshot of Home Server's storage console, showing drives in the pool

Another benefit is that drive failure doesn’t mean a total filesystem meltdown (if you don’t have mirroring). It just means that the (admittedly, randomly assorted) files on that particular volume are temporarily unavailable until you can bring that drive back online (recover, Ghost, etc). So if you kick a cable by accident, your whole server wouldn’t go down… it’ll just make a few files unavailable until you reconnect the drive. On the subject of drive removal, you can also add and remove volumes on the fly – yes, REMOVE. You can instruct DE to remove a drive, and it’ll move all the data off that drive onto other members of the pool, and allow you to remove that drive with zero effect on data. You can add a drive by simply plugging in a drive of ANY size, and adding it to the pool. It’ll use it for additional storage.

I really think Drive Extender will revolutionize the way RAID is used in businesses… if it can get any attention outside the HTPC and home user circles. I’m certainly not a fan of anything Microsoft has been doing lately (well, 7 is a good “step” back in the right direction), but Home Server is all the right things in the right places. Maybe we’ll see this technology come into the IT world sometime soon.



  1. Not really. Linux has had Logical Volume Manager since 1998, 9 years ahead of Microsoft. Same concept, different implementation. It’s not going to revolutionize RAID in the enterprise. RAID is about the balance of performance and availability. LVM/DE just make partitions bigger — RAID0 without alternating drives. It most certainly is a valid solution, but it’s best suited for home users, small business, and other applications where availability is not overly critical.

    • Well, yeah… on linux. On Windows, which is at the heart of many medium-to-large companies, there’s either hardware RAID or nothing.

      I’d also like to think that DE isn’t really “at home” in the home environment, and that it’d be better implemented on a large scale… a few bugs to be worked out, sure (like “total size” still being reported as the landing zone drive size – most of the time it shows 300+GB free on a 120GB drive), but really, it would shine brightest when multiple file requests are thrown at it at the same time.

      Thanks for the comment though! You’re the first person to comment on my little blog 🙂

  2. Microsoft has *created* a revolutionary technology? Where? RAID already exists. Using files as underlying parts of a RAID already exists. And finally, ZFS manages storage componsed of M disks letting Y filesystems use it, so even the smallest filesystem receives full advantage of all the performance (spindles) and redundancy (RAID) characteristics of storage pool.

    So your initial claim was just to bold, just too wrong. Microsoft has not revolutionized anything. They’ve copied. Nothing wrong with that, just don’t be blind fanboy and give them credit for the idea.

    • Hey, just because you didn’t read the article doesn’t mean I’m a fanboy. I’d say I’m anything but.

      Point me to a single OS or implementation that merges several independent volumes (filesystems) into one file structure… ZFS just doesn’t sound like “it” either.

      • ZFS multi-disk redundancy: check.
        ZFS arbitrary storage expansion: check.
        ZFS single folder namespace: check.

        Please don’t go around pretending to know what is revolutionary when obviously you do not.

    • But being able to access different files on the same “virtual volume” at the same time from different disks?

      Plus, the fact that it’s not on Windows still makes it practically irrelevant… large companies use Windows, while Web services use *nix. May be relevant to Web services, but not in the “corporate environment”…

      • uhm yeah. multiple files, multiple filesystems, all concurrently. You must be a noob to real computing otherwise Disk Extender wouldn’t have impressed you so.

        Why do you now try to steer this towards a windows-only solution? I mean you just said they would easily revolutionize the entire IT industry. Any experienced IT professional knows the vast majority of filesystem storage is not on Windows servers anyways. And you say that non-windows fileservers are not relevant? Ha!

  3. I agree with the author the drive extender is a exelent new peice of technology that does impress as it acheives on basic equipment ie sata or ide drives to accheive this on sczi uses exotic and expensive hardware and is not user freindly. I do belive this will be more biased to SOHO and home use, but I also understand it may not be sutible to bigger businesses or enterprise.

    Please note this product is a good product and no I am not a fanboy microsoft have great products as will as some junk.

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