The Technology of WHS

Because WHS is a retooled version of Windows Server 2003, it's at times a sharp contrast to Vista, or even XP for that matter. Microsoft has attempted to put a lot of attention on WHS's headless operation mode, which allows a WHS server to run without a keyboard or monitor (but not a video card). For this purpose WHS is very much a server, as all administration tasks can be handled by the clients via a special Remote Desktop application while the server sits in a corner gathering dust. Microsoft even goes so far as discouraging use of the server directly both in the manual and on the warning dialog that pops up on the desktop of the server, in an effort to keep users inside the confines of the able but simple administrative client.

WHS also inherits Server 2003's low by modern standards system requirements, requiring as little as a 1ghz P3/Athlon processor and 512MB of RAM. Although systems shipping from computer vendors will be far more powerful, it's clear from the start that when it comes to the enthusiast market, Microsoft sees this as going on an old computer that's outlived its usefulness as a primary computer but is still well prepared for server tasks that will be limited by disk I/O and not CPU cycles or memory.

The final significant piece of technology to come over from Server 2003 is its security. By default WHS is locked down hard, bringing over the security enhancements that made Server 2003 harder to break into through a reduction in exposed services to attack. Microsoft is taking some liberties here in assuming that the server will be behind a naturally protected network with a NAT/firewall at the head. When properly configured, what is exposed to the internet (and not by default) is solely Internet Information Server 6.0, which has proven to be a hard target to break into (at least compared to the laughable IIS 5.0). Microsoft even goes so far as requiring strong passwords on any accounts that will be accessible from the internet (7 characters; uppercase, lowercase, and numeric characters required), which shows that some thought went into this.

Although Server 2003 predates Vista, the development team did manage to steal a handful of technologies from the fledgling operating system. Those tired of floppy disks will be ecstatic to find that Vista's far superior installation loader is used, allowing drivers to be loaded off of flash memory rather than floppy disks. The rest of the installer is still the traditional file-copy installer however, so WHS does not install quickly like Vista, although in Microsoft's defense users will ideally not be installing a server operating system as frequently.

Hardware and driver compatibility is something that needs to be mentioned as it's a natural result of using a server OS as the base. Simply put, a piece of hardware needs to be Server 2003 compatible to be WHS compatible. For critical components such as motherboards and video cards this shouldn't generally be a problem, although on the AMD side specifically there are some Athlon/Athlon-XP era boards that never got proper Server 2003 support. Many RAID controllers however aren't supported in spite of the availability of drivers due to WHS's unique method of handling disk drives.

Putting a new face on Server 2003 wouldn't be enough to make it capable of handling the duties of WHS in Microsoft's eyes, so among the new technologies in WHS and the one most paramount by far to its operation is what Microsoft is calling Windows Home Server Drive Extender (WHSDE). WHSDE is a new abstraction layer that sits between the various WHS services and the hardware, creating a common storage pool out of all of the available disks on the system, similar to the JBOD mode on some RAID controllers. This means that files & folders are no longer constrained by the size of any individual drive (from an end-user perspective you never even see things as drives, just folders) and instead WHSDE distributes files to drives based on how it believes space would best be allocated.

Furthermore, the storage pool is almost completely dynamic, in direct opposition to most JBOD/RAID setups. New drives can be added to the storage pool without disrupting the server, allowing the pool to be easily and continuously expanded to meet the data retention needs of the server. Drives can also be removed from the pool with a little more effort, as WHS can be informed to move all of the data off of a drive (assuming there's space elsewhere) so that the drive can be disconnected without interrupting the pool. While this isn't a completely new feature as various *nix systems have implemented similar features, this is the first we've seen it on Windows, and certainly in the running for the easiest to use implementation of such a feature.

Finally, WHSDE has a very interesting data protection feature that in many ways is a poor man's RAID 1, and yet smarter at the same time. By default WHSDE is constantly balancing all the drives so that no single drive is storing a larger percentage of data than another, so in the case of a drive failure the data lost will be an equal fraction of the data. More importantly however folders can be marked as needing additional protection (folder duplication), at which point WHSDE will make sure that the contents of that folder are on at least two separate drives when doing its balancing act. This is what makes WHSDE a poor man's RAID 1, as this balancing isn't done in real time and there's not immediately a copy of every single bit, but it's also smarter because this kind of protection is possible even among mismatched disks, disks on different controllers, external versus internal disks, etc. It offers slightly less protection than RAID 1, but as a tradeoff it's a lot more forgiving too.

At the end of the day WHSDE is really what makes WHS work and more than just a cut-down version of Server 2003. Just having a common storage pool alone makes WHS far easier to use with large amounts of data that don't fit on a single drive, and the extremely dynamic/forgiving nature of how drives and replication are handled becomes the distinguishing factor. WHSDE makes WHS far superior to any other version of Windows for storing and protecting data, and this is what gives it the ability to be a great server for home use. For enthusiasts, we suspect it will be the most attractive feature of WHS, for use as a file server.

It's also worth noting that this is the reason that WHS has very limited RAID support. Since all disks are assimilated by WHS, any RAID setups requiring configuration in Windows will fail. Only RAID setups done completely at the BIOS level (which normally requires higher-end RAID controllers) will work under WHS, and even then Microsoft discourages the use of such RAID setups in favor of the protection offered by WHS natively. RAID 5 users may want to ignore Microsoft on this however, as WHS's protection isn't as efficient as RAID 5, and it's slower due to WHS needing to balance data.

Index The Interface of WHS
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  • ATWindsor - Sunday, September 9, 2007 - link

    All NAS-boxes have horrible performance. (at least all I have seen). It hardly seems fair to use benchmarks from them, when this is a "Proper" computer, there are plenty of benchmarks from software raid 5 run on "real" computers to find, see this for instance:

    http://www.tomshardware.com/2004/11/19/using_windo...">http://www.tomshardware.com/2004/11/19/...appen/pa...

    MDADM is as far as i know even faster, hower for whs it would likely be built on the software-raid of win2003.
    Reply
  • Gholam - Sunday, September 9, 2007 - link

    All NAS-boxes have horrible performance.

    Wrong. Proper NAS boxes have superb performance. Look at NetApp FAS270 for example. Of course a FAS270 in a typical configuration will run you in the $20,000-30,000 range.

    That Tom's Hardware test is running a 2.8GHz CPU. http://www.pcpro.co.uk/reviews/121499/tranquil-t7h...">This WHS box is running a 1.3GHz VIA C7, for example.

    Also, WHS is designed to be easily and transparently expandable by end-user using external drives. Please show me a RAID setup of any kind that will work in a mixed ATA/SATA/USB/FireWire configuration with drives of varying sizes.
    Reply
  • ATWindsor - Sunday, September 9, 2007 - link

    Ok, all consumer NAS-boxes then, I thought that much was implicit. It doesn't matter anyway, the point is that your comparison to a box like that isn't very good when it comes to "proving" that software-raid automatically has bad performance.

    A lot of boxes with WHS will be using a CPU that is better than a 1.3 Via, if the hardware isn't suited for the job, then you just don't run a software raid5, it's that easy.

    I don't see how the WHS storage-pool is incompatible with raid as a concept, a raid-array presents itself as a single drive, more or less, wich can be merged into the storagepool if one feels like it.
    Reply
  • Gholam - Monday, September 10, 2007 - link

    Infrant ReadyNAS NV+ is a consumer level NAS. However, it's built on an SBC running a 1.4GHz Celeron M ULV, and in actual testing outperforms many self-built systems. On the other hand, it also costs over $1000 without drives. Reply
  • ATWindsor - Monday, September 10, 2007 - link

    The benches I have seen points to a read-performance of 30 MB/s give or take lets say 10 MB, thats hardly good performance, it doesn't even outperform a single drive. One can easily build a software raid with several times better speed. Reply
  • Gholam - Sunday, September 9, 2007 - link

    WHS is made to run on low-power, low-end and old hardware; calculating parity blocks in software is bad enough on a modern desktop CPU, an old PIII/800 or a VIA C3/C7 (present in some OEM WHS box implementations) will get murdered.

    In addition, recovering data from a failed RAID5 array is quite difficult, requiring specialized (and expensive) software as well as user expertise. Recovering data from a failed WHS box with duplication is as simple as mounting the drives separately.
    Reply
  • ATWindsor - Sunday, September 9, 2007 - link

    The raid will not fail before two drives goes down, if that happens in WHS, you still need to run recovery-software and hope to get out data. WHS will be run on diffrent kinds of systems, even the cheapest of CPUs today are pretty powerful. More than powerful enough to get reasonable spped on raid5. Why limit WHS in this way? That is exactly the problem I'm adressing, the lack of flexibility, the reasoning that all WHS-users have the same needs, I think a pretty large number of WHS-machines wich poeple build themself will have performance several times higher then a P3@800, if not most. Reply
  • Gholam - Sunday, September 9, 2007 - link

    The raid will not fail before two drives goes down

    Oh how I WISH that was true. Let me give you a recent example I've dealt with. HP/Compaq ProLiant ML370G2 with SmartArray something (641? don't remember) running a 4x36 RAID5 array, Novell Netware 5.0. DLT VS80 tape backup drive. Worked for 4 years or so, then the tape died. Took the organization in question 4 months to buy a new one, LTO-2 - which means they've had 4 months without backups. Downed the server, connected the new tape, booted - oops, doesn't boot. Their "IT guy", in his infinite wisdom, connected the tape to the RAID controller, instead of onboard SCSI - which nuked the array. It didn't go anywhere, the controller didn't even report any errors, but NWFS crashed hard. They ended up rolling back to 4 months old backups because pulling data out of a corrupt RAID5 array would've cost several thousands.

    I work for a small company that specializes in IT outsourcing for small and medium businesses - basically shops that are too small to afford a dedicated IT department, and we give them the entire solution: hardware, software, installation, integration, advisory, support, etc - and I've got many stories such as this one. We also deal with home users, but not as much.

    This said, I don't consider RAID5 a suitable for home use, at least not yet. It's too expensive and dangerous - mirroring files across a bunch of drives is cheaper and easier. Also, as far as I understand, when a drive in WHS drive pool fails, it automatically syncs protected folders into free space on remaining drives, so the window where your data is vulnerable is quite small. RAID5, on the other hand, will be vulnerable until you replace the drive (which can take days or even weeks) and then until it finishes rebuilding (which can also take a very long time on a large array). You can keep a hotspare, but then you'll be eating up another drive - in case of 4 drives, RAID5+hotspare eats you the same 50% as RAID1/RAID10 - while WHS mirroring makes your entire free space function as hot spare.
    Reply
  • ATWindsor - Sunday, September 9, 2007 - link

    Hardly a very plausible scenario for a home user, of course a RAID can go down if you mess it up, but you can just as easily mess up non-raided drives to the point that running recovery-software is needed, when it comes to normal drive-failiures two of them have to die.

    If you only need 2 Drives worth of storage, you might as well mirror, but when you need for instance 10, it adds up, but drive-cost, electricity PSU-size and physical size (especially if you want a backuo-machine in adition, I would never keep my data on only one computer like that). If the syncing is going to work,you also need to have at least a disk of usalble free space, so you basically need to "waste" a whole disk on that to if you wnat to get hot-spare-functionality.



    Reply
  • Gholam - Monday, September 10, 2007 - link

    Hardly a very plausible scenario for a home user, of course a RAID can go down if you mess it up, but you can just as easily mess up non-raided drives to the point that running recovery-software is needed, when it comes to normal drive-failiures two of them have to die.

    Not quite. WHS balances data between drives, so if one of them becomes corrupt and one of the copies of your protected data is gone, you can still access it on the other - no extra tools required, just mount the drive in a Windows system. You will only lose it if both drives become corrupt simultaneously.

    If the syncing is going to work,you also need to have at least a disk of usalble free space, so you basically need to "waste" a whole disk on that to if you wnat to get hot-spare-functionality.

    Again, not quite. Since you protect the data on a per-folder basis, your free space requirement depends on the actual amount of data you're keeping redundant, not the total, and there's little point in wasting redundant storage on backups - they're redundancy in and of themselves.
    Reply

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