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Are Windows Dynamic Disks Reliable?

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mwb1100:
Just for learning purposes I was using a windows dynamic disk software RAID 1 configuration (mirrored disks).  At some point I decided I didn't need that configuration anymore and I wanted to repurpose one of the disks.  I didn't need the data on the volume anymore, so I simply pulled one of the disks (not a hot-unplug - a shutdown/unplug operation).  I figured that this should look like a massive failure of one of the disks in the mirror.  So just to see how well I'd be able to get the data off I tried doing that with the remaining disk.

I did not spend a whole lot of time on it (it was just an experiment), but I was unable to do it easily.  In fairness, I did not try rebuilding the mirror with another disk, which is probably the supported way of fixing a failed mirror set.  In conclusion I'm not sure what my experience really says about dynamic disks, since I wasn't doing a serious experiment/following proper procedures, but it didn't leave me feeling confident I'd be able to handle a failure without loss - at least not without considerably more study or training.

The other thing I'd wonder about is how well other tools (especially image backups) work with dynamic discs; they didn't back in 2000.  I'd hope they would now, but I'm certainly not sure they do (or do well).

I'd say if you want to try using it, run through a test of a failure and see what's involved in making things right.  Otherwise you're likely to be completely hosed when you have an actual failure, so what would the point have been?  A virtual machine setup should make the tests pretty easy to run though to get the experience, but I'd still do at least one run though with non-virtual hardware - I'm not sure why other than paranoia.

edit:  correct RAID 0 -> RAID 1.  To clarify - I was using a mirrored disk set.

Carol Haynes:
A lot of backup utilities don't support dynamic disks - especially if you want imaging solutions.

Personally I would avoid 'soft' dynamic disks.

I have used RAID 0, 1 in the past with no problems - but not much advantage either. I think RAID 0 is quite useful if you do a lot of intensive data processing (like recoding video or lots of audio processing) as the speed advantage is quite good - but you are better setting up a small RAID set on a couple of separate identical hard discs and using it for run time processing and offloading the data for storage. Keep the RAID array clean for speed. By the way imaging backup apps work fine for RAID 0 and 1.

FWIW I don't think RAID 1 is worth the hassle on home computers as you may as well have a standard IDE (SATA or PATA) and an external drive to do regular incremental backups. It isn't slower to rebuild a dead disk and in use it is a bit faster (particularly if you write a lot of data). If you need a constant backup you can use a versioned backup solution like AutoSave or the freebie from Iomega which mirrors every disc write to an alternative location (and you can limit the number of revisions).

4wd:
I tried RAID 0 when I initially had a motherboard that supported it, (EPoX 9NDA3+), and I found that there is absolutely no speed advantage at all.  As soon as more than one process wanted data off of the same array as another process, it was exactly the same as using a single drive.

IMHO, RAID 0 is pretty much useless for the home environment unless you are using it for a media server but even then it's no better than a single drive and you've doubled your chances of losing your data - OR - you're one of those strange people to whom benchmarks are the be-all and end-all of everything.

RAID 1 is useful IF you want to waste a drive, (home environment again), and power - an extra drive just sitting there so it can just be a backup to another drive.  Unless you're running mission-critical software at home, (you're crazy if you are), then it's pointless.

JBOD is another way to ensure you will lose ALL your data if one drive dies.

As Carol said, get an external drive to do your backups on - I'll expand on this and say use a NAS of some kind.

FWIW, I do a lot of digital video capture/editing from my DVC, and a 4200RPM drive is fast enough to handle the video capture via firewire and if you want to ensure access speed for fast re(en)coding, do it from one drive to another on a different controller preferably.

Just thought of one area where RAID 0 might be useful at home - games.  With their multi-MB resource files, RAID 0 would allow them to load a fair bit faster and since game processes usually take >90% of the CPU time, other processes are less likely to cause much drive thrashing.

f0dder:
Humm, wouldn't say RAID STRIPE (I prefer the names to the numbers, to avoid confusion) is much of an advantage during video encoding, since you're doing some very CPU- rather than disk-intensive operations. But for video editing before the encoding process, sure thing. But I dunno how useful it is for stuff other than that, really. "But, game load speeds should drop!" - yeah well, I put the entire of "Thief 3: Deadly Shadows" on a RAM disk, which is plenty faster than the fastest RAID stripe you can muster, and that didn't do anything for game load speed. And seek-time can go up when using raid. And then you have the "all data dead on single drive failure" aspect of STRIPE... ugh.

I don't agree that RAID MIRROR is too much hassle for home setups, and you shouldn't be comparing it to backups - those are two entirely different things. A mirror won't help you against stupid accidents or malware, a good backup solution can do that (if you disconnect the backup location once done). At the other hand, if you only backup once per day, you risk losing a whole day's work if you don't have a mirror.

RAID MIRROR and a proper backup strategy goes hand in hand, really. Oh, and a decent RAID MIRROR solution will give about the same write speed as a single drive (possibly a slight bit slower), but give about double the read speed (ie, you get striped reads). Iirc Intel RAID Matrix storage does this, nvidia's NForce4 certainly doesn't (my mirror back then was noticably slower than a single disk, for reads as well as writes >_<).

Btw., with a RAID-STRIPE setup I did find that things like extracting big .RAR archives with same source and destination went a lot better than on a single disk (ie., handles "stressful workloads" better than a single drive), but still worwse than having distinct physical disks for source and destination.

Carol Haynes:
There is no doubt that RAID-0 gives a good performance boost in disk intensive activities (heck shoving your Windows page file onto a RAID 0 array with less than 1Gb memory gives a measurable increase in system speed if you like to have loads of apps running). I did some measurements on my old system before it went caput and reckon that I got about 60% increase in disk throughput but you are right disk speed is not the only factor and you have to choose your applications well to see a worthwhile improvement on a home system.

RAID 1 is actually slower with disk writing than a single disk (though faster on disk read). I don't really see the point though as data integrity is the only benefit with RAID 1 and that is easily acheivable in realtime with continuous backup system. For example, AutoSave intercepts every disk write and mirrors a version of the new/altered file to an alternative location - this gives the same benefits of RAID 1 but adds the benefit of realtime file versioning (you can set it to keep n updated copies of files so you can instantly receive n generations of file changes - nuch more useful than RAID mirroring). Combined with frequent incremental images and you have a system that is pretty immune to malware and quickly restored on error.

There is a place for RAID 0 and RAID 1 (and indeed RAID 0+1 and all the parity check versions of RAID) but to benefit you really need a specifically targetted application and keep your system optimised for that application. A good example is setting up a specialist Audio/Visual Studio or high end professional PhotoShop setup where you are producing and processing stupendously large files.

For day to day use RAID is more of a headache than a help, and consumer level interfaces aren't particularly reliable (and IME mobos that include RAID interfaces are the least reliable).

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