Are Windows Dynamic Disks Reliable?

[tinjaw]

I just realized that for years and years I have avoided Windows Dynamic Disks because of bad reports when they first came on the market. I have also never worked for a company or known anybody that uses them.

I was wondering if they have become as reliable as any other software RAID solution. Does anybody have any first or second hand experience with them? Is there any clear-cut reason why I should avoid using Dynamic Disks? I understand their proprietary nature and that it takes a lot of aggravation to fix them if they go bad.

[nite_monkey]

The only experience I have had with dynamic disks is with my virtual machine, I have two virtual drives spanned to one drive. But I just did that after reading your post, I wanted to see how dynamic disks worked.

[wraith808]

The only experience I had was bad... but that was when it first came on the market.  I lost a *lot* of data because of them, and became scarred against using RAID.  I don't know about currently- I haven't touched them since.

[f0dder]

The only experience I had was bad... but that was when it first came on the market.  I lost a *lot* of data because of them, and became scarred against using RAID.  I don't know about currently- I haven't touched them since.

-wraith808 (February 24, 2008, 02:36 PM)

When was that, Windows 2000 or NT4? And what happened?

[wraith808]

Windows 2000.  I'm not sure of the exact details of what happened, but during a routine scandisk, one of the drives had a bad sector, and I tried to mark it as such.  The next few days, my drive was acting wonky, so I got a Jaz drive and started to offload the most critical data.  During the second disk the copy functions started failing, so I tried to back the data up to another drive on my network, but couldn't copy anything.  I rebooted, and windows would recognize the drives, but the partition was gone.  At first I thought the drive had gone bad, but after I did a low level format and ran Norton on the disks, they were fine- In fact, I still use them (just not for critical data).

[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).

[f0dder]

RAID 1 is actually slower with disk writing than a single disk (though faster on disk read).

-Carol Haynes (February 25, 2008, 08:26 PM)

With good systems, you shouldn't have a really noticable degradation in write speed compared to a single-disk config... and, the flipside, on bad systems you won't see any improvement for read speed. Depends on the RAID implementation. NForce4 sucks, Intel RAID Matrix rocks

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.

-Carol Haynes (February 25, 2008, 08:26 PM)

Yup, data integrity is the reason you should choose RAID MIRROR, but ~doubling read speed doesn't hurt

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).

-Carol Haynes (February 25, 2008, 08:26 PM)

Yes, that's certianly cute and you don't get that with a raid mirror. But if the realtime sync/backup is implemented without a filter driver, performance will be hellish for large files...

I personally wouldn't trust my data on anything but raid mirror, not even the fancy-pants parity schemes either - RAID-5 (the typical parity based RAID mode) can still only save you form a single crashing disk, and rebuilding is an expensive operation... I've heard more than one horror story where a second drive fails during rebuild, and then you're S-O-L.

My current setup is to have a 400gig raid mirror on my fileserver, and... ummm... not doing any automated backups of my workstation >_<. I haven't decided on a backup app yet, as I haven't found any I really like. But the goal is definitely to do incremental backups to the fileserver. I already have my most important stuff there, though, which is my source code - and that is automatically backed up with rsnapshot.

I plan to upgrade to a better motherboard in a while, since this board doesn't have the intel RAID matrix - once I do, I'll group the two 74gig raptors, and split into a MIRROR and a STRIPE part (that's the beauty of raid matrix, it allows you to have both a mirror and a stripe with only two disks). Mirror for all my important data, stripe for windows+apps+games and "scratchpad use" - in other words, stuff it doesn't hurt losing.

[4wd]

Humm, wouldn't say RAID STRIPE (I prefer the names to the numbers, to avoid confusion)

-f0dder (February 25, 2008, 07:19 PM)

I prefer the numbers for exactly the same reason  

But for video editing before the encoding process, sure thing.

From my experience using it with video capture from a digital video camera, it isn't.  Capturing to a single drive is no problem because the bandwidth required for capture is well below typical drive throughput, (hence where I said a 4200RPM drive is fast enough - if you have problems capturing, the fault generally lies elsewhere, eg. PIO, background processes).  Editing from one source drive to a separate destination drive will beat a RAID 0 array every time simply because there is no drive thrashing.  The only way it would be better is to go from one RAID 0 to another RAID 0 and/or using better drives - desktop drives are no match for enterprise drives that are manufactured for the increased requests.

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.

I don't think it would change 'game load speed' but what about loading of data during game play?  I'm talking about those games that pause every so often to load in the next >200MB resource file.

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.

When I refer to 'home environment' I don't include a business, (which is what your "whole day's work" implies to me), that runs from home - that's no different from a business in a store or a corporation, (except in size), AFAIC - and as such your backup strategy should be more robust.

When I refer to home environment it is reference to the generic home PC that's used for games, internet, the odd word processing, picture collections, etc.  For that, I really don't see any need for RAID.  Not even for video editing which I do at home on my general purpose PC.

RAID MIRROR and a proper backup strategy goes hand in hand, really.

Yep, no problem with this for business applications, (and those that are just plain paranoid  ).  But for generic home applications a decent backup setup is more than adequate and a lot less hassle when it comes to restoration in the case of a fault.

[f0dder]

From my experience using it with video capture from a digital video camera, it isn't.  Capturing to a single drive is no problem because the bandwidth required for capture is well below typical drive throughput, (hence where I said a 4200RPM drive is fast enough - if you have problems capturing, the fault generally lies elsewhere, eg. PIO, background processes).

-4wd (February 25, 2008, 09:05 PM)

Capturing is one thing, but editing, scrolling through frames etc... I would think a stripe makes things a bit more comfortable there? And whether a 4200rpm drive is appropriate for capture probably also depends on the source format... how much throughput does HD video require?

I don't think it would change 'game load speed' but what about loading of data during game play?  I'm talking about those games that pause every so often to load in the next >200MB resource file.

-4wd (February 25, 2008, 09:05 PM)

I thought it would have helped there, since many games seem to have relatively low CPU usage while loading, indicating that they're disk bound. But my RAMdisk try with Thief3 was disappointing, and a "die/reload/try-again/die/..." cycle in half-life2 where everything should be in disk cache (8 gigs of ram...) it was pretty much the same results, so I don't think a stripe would help much there.

I wonder what the games are doing during load, if it's neither CPU nor disk I/O bound. Perhaps something to do wrt. uploading textures to the GPU, but that's supposed to be super fast (PCI-e x16 has quite some bandwidth). I really don't know

When I refer to 'home environment' I don't include a business, (which is what your "whole day's work" implies to me), that runs from home - that's no different from a business in a store or a corporation, (except in size), AFAIC - and as such your backup strategy should be more robust.

-4wd (February 25, 2008, 09:05 PM)

I know my backup strategy isn't robust enough

When I refer to home environment it is reference to the generic home PC that's used for games, internet, the odd word processing, picture collections, etc.  For that, I really don't see any need for RAID.  Not even for video editing which I do at home on my general purpose PC.

-4wd (February 25, 2008, 09:05 PM)

As long as a solid backup strategy is in place, a mirror wouldn't be necessary for that kind of home use. But a backup strategy certainly is, lots of people have irreplacable data on their systems now, and don't even think about the possibility of their drive dying... photo albums, anyone?

Yep, no problem with this for business applications, (and those that are just plain paranoid  ).  But for generic home applications a decent backup setup is more than adequate and a lot less hassle when it comes to restoration in the case of a fault.

-4wd (February 25, 2008, 09:05 PM)

Agreed. I'm probably borderline paranoid . But I've experienced losing 3 years of programming and stuff (a mirror wouldn't have helped me then though, but that opened my eyes), and I've been very close to losing a lot of work due to a drive failure.

Anyway, the RAID MIRROR is crucial for my fileserver, since that's where I store the backups (yeah, I do have manual backups of a lot of stuff, I still need an automated scheme though ).

[4wd]

Anyway, the RAID MIRROR is crucial for my fileserver, since that's where I store the backups (yeah, I do have manual backups of a lot of stuff, I still need an automated scheme though ).

-f0dder (February 26, 2008, 05:28 AM)

How about SyncBackSE, (since DC have a discount in place at the moment) persuaded me to upgrade from the free version