Windows Home Server, redefining the idea of RAIDMay 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.
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.