Raid Disk

Hi

Seen a lot here and there about computer music haven't read no where near all the threads so don't know if it's been mentioned, but an essential consideration I would say, modern reliability of hard drives or not.

Stuart

 

Erm I am not sure what question you are asking there...
I know all about RAID arrays; if that is what you were asking about?

If you phrase a question I will do what i can to help (aslong as you answer my thread!)

 

Seagate offer a five year guarantee. That's more than Naim do on their CD players and as the lasers seem to go after 3 years I'd say HDD was a safer bet.

Meanwhile if my HDD did fail the datas not lost but I'd have to load it all back on again. Worth another £250? Probably

 

Modern drives have very good reliability. The computer I'm typing this on has two drives which have been working quite hard for 4 years! I've had dozens of disks pass through my hands and have seen just one drive (controller) failure - which was actually user error. Remarkably enough, I still managed to recover the data off the drive by swapping a controller card onto the disc from an identical drive.

What is much more of a concern IMHO is that the system on which the data is stored typically runs windows as is a multi-purpose box used for browsing etc. It is much more likely that this box will go pearshaped because of a hole in explorer rather than a disc failure, and that virus spread via email (downloaded by user request) means that firewalls are not much use. That some folks do without firewalls (or misconfigure them) or have trivially insecure wireless access points is more likely to be a problem.

RAID although it is a good technique for covering disc failure but is NO SUBSTITUTE for proper backups. You can still erroneously delete files from a raid array!

I thought long and hard about whether to back up my music server. And there's no good (cheap) backup solution for 400GB drives. In the end I opted to consider the shiney silver discs as the backup and go through the ripping process again should the worst happen.

 

i think oedipus has summed it up for me too. my wardrobe full of cd's is my backup. sure it'd be a pain to have to re-rip them all but there isn;t really another reasonable alternative (unless i buy a terrabyte external drive and then have it sitting around doing nothing which i'd rather not do). this is one thing blu ray will be very useful for. with 25 gig per disk recordable i could back up my entire collection (at present) on about 20 disks. still a lot but less than the 800 or so on cd. still that'll probably be crippled with over zealous drm so maybe scratch that possibility.
cheers


julian

 

by far the greatest cause for failed hard disks is mishandling - and it doesnt necessarily have to be by the end user! I personaly would NEVER buy any hard drives from a computer fair.

 

If you are going to use the computer primarily as a music server and worried about virus through emails or explorer then it may be more useful to have Linux as the operating system.

There are no where near as many people trying to screw linux users up as there are windows users. Things like the squeezebox also work on Linux and there are , in some peoples opinions, better/safer browsers than Explorer.

Plus being an oldhead IT person command lines are so much better than this point and click rubbish.

 

Especially when they were written in Latin.

 

Tom, I would say that were I to follow this path I personally would use a networked disk array.

eg. starting with 6 * 250 GB SATA disks configured as RAID5 = 1TB of logical space and has both performance and redundancy benefits - though I dont think the enhanced read speed would be of any benefit unless I also used it for streaming video.

The main benefit - depending upon how it is approached - that a good NAS RAID array would allow you to keep adding disks and thus extending your capacity - 12 disks and approx 2TB of storage. But you are obliged to use disks of identical size so if I started with 250GB disks I'm prevented from exploiting larger capacity drives in the future as they fall in price.

So perhaps starting with 3 * 400GB disks might be worth it even though the cost is much higher at the start.

 

Don't overlook the fact that one of the core benefits of a RAID array is to allow you to have a logical storage that exceeds the capaicty of one large disk - eg. a 2TB array instead of a 400GB disk - the redundancy should also not be overlooked - a disk goes and yes it may be under warranty - you get a new disk with no arguments but no compensation for your time or the inconvenience.

 

I think smudge was just raising the subject as a consideration, not asking for help. Just incidentally - do you really know ALL about RAID arrays? Bold claim, but if you do you might be a useful reference point when we (our company) get stuck.

 

anyone choosing RAID - make sure you dont scrimp on the raid controller. SATA RAID is a nice cheap way of getting RAID benefits - but I hope my local hospital doesnt rely on sata raids for storage! OK for music though.

 

Have you had a bad experience? To my mind SATA solutions appear to be highly reliable and some of the SATA 6 channel controllers seem peachy - 6 * 150 Mbps seems highly convincing. SCSI suppliers are naturally obliged to imply SATA isnt a business class solution but then what else can they say to pursuade people they need expensive SCSI solutions instead of cost effective SATA alternatives. With appropriate redundancy a SATA solution is surely as good?

 

SCSI typicaly has double the mtbf spec over sata plus some other protocol benefits hence the reason for cost and use in mission critical systems. sata is still excellent and offers real benefits at a low cost - perfect for home and non critical systems.

 

Doesn't serial ATA RAID use CPU power to do some of its trickery though? As far as I know the controller on the mobo will operate on its own in a slow speed for DOS and such like but to get the full speed you need to use CPU power.

With modern CPU's I don't really see it as a problem, but it still seems 'cheeky'!

 

No you wouldn't It seems like a good idea, but you haven't thought it through..

Network attached storage is way, way expensive for extensible cabinets. It comes with redundant power supplies, and huge fans - with huge amounts of noise, consumes a fair bit of space and generally needs to be in an air-conditioned/temperature controlled room. The cabinet alone (no disks) is probably upwards of $5K for a 12 slot cage.

Next, you've got the learning curve. Configuring one of these monsters assumes you have some clue, or are prepared to work through a fair sized manual. And you have to configure the client...

For reliability and fast repair, you typically buy an eye-wateringly expensive service contract - which is why these things get fixed in 4 hours. If your doing this at home, you could keep spare disks lying around. But I might add that it's not always a disk failure that is the problem - controllers fail too, which is why redundant controller configuration is preferred - more $$$.

When it does go wrong, you'll have forgotten what the manual says, and there's a good chance that you'll yank the wrong disk out of the array (a working one rather than the dead one). You can of course spend more $$$ for an more intelligent cage with flashing lights - which are sold as idiot proof (largely ignoring the creativity of idiots )

You also have the issue of how to attach the beast: the "network" might be fibrechannel after all..

PCI RAID controller have a number of maladies themselves - they are more of a placebo than an actual solution - as they don't have any of the high availability features of "real" raid arrays.

Building a reliable storage solution is much, much more difficult than lashing together a commodity PC, a bunch of disks and a PCI raid controller - it's why companies like Hitachi/IBM/etc charge big bucks for those boxes..

And at the end of the day, RAID provides no backup mechanism, so if you delete something it's gone - user error (not disk failure) is the #1 reason why data is lost.

 

Seems like a good idea because it is and, perhaps surprisingly, I have thought it through.

Depends what you were trying to buy but your assumptions are not true in my experience. Though, my suggestion does rest on the assumption that such a solution would require greater investment than the simple examples, but if I sell my digital source I would be well on the way to funding the alternative, though the cost benefits, say, Julian's or Tom's solutions, do diminish somewhat. However there are ways and means to aquire and configure a 12 disk cage - starting with three disks for what I consider to be bargain prices.

Talking more simply - a brand new Dell server with space for six disks (starting with three) and a 6 channel SATA RAID controller can be had for low money (we just bought one) - this would present the server and the architecture to end up with 6 * 250 GB (or even 6 * 400 GB disks) in a pretty well designed machine and for just a bit more than I could get for my player (c.1500). Yes there's the squeezebox to consider though Wifi is already in place.

Learning curve already conquered, though I take your point to an extent with novices.

We're not talking mission critical financials data server and I think you aer being either pesamistic or a little negative.

All a little OTT.

Indeed, backup is expensive by comparison and limited, but then you have the CD's right?

 

i could be wrong but there seems to be only 3 advantages to using raid..
1) protection against drive failure - but you loose a lot of starage space and you've still got your cd's haven;t you?

2) faster access (striping?) - this is hardly critical when streaming music - or even video for that matter - maybe when we get to holographics but then the sota should have advanced.

3) a bigger logical drive. - this kind of makes sense but it really pretty pointless with slimserver as you designate a single music directory and can have shortcuts to other directories inside that 'root'. i have 2 hdd's one with artists 0-9 and 0-g and the other with h-z. i have 2 links to the root folders on each drive in my 'my music' folder and slimserver works just dandy.

to my mind raid just isn;t necessary when dealing with a system for music playback. what is necessary (or would be nice) is a removable backup method which is inexpensive and wieldy - for my money even blu ray disks won;t really be large enough.

cheers


julian

 

Well drive failure redundancy is worth something and with RAID5 and 6 disks you lose the capacity of one disk.

True - the performance benefit isnt worth it for music, though I would have thought it is for streaming video? Not sure.

Very compelling point, I didnt realise. In which case the argument for a bigger logical through RAID is not really significant. Thanks for the info Julian.

 

Your confusing redundancy with reliability. Putting 6 drives on a raid controller gives you redundancy, but there are a number of other features that are needed to turn that box into a reliable system. The only failure your protecting against so far is a single disc failure. Now, the things you class as "over the top" and "pessimistic" (multiple controllers and power supplies) cover other kinds of failure, which do actually happen in practice. When a failure does happen, you want the best "idiot proof" recovery software you can afford, and that costs money - skimp on the controller and software and those extra disk save you nothing. In fact a mishap in recovery means you loose all your data rather than a single drive! I should also add that the assumption that there will be a "single point of failure" has been the undoing of a number of recovery schemes - correlated failures happen, like when a failing power supply takes out TWO drives.

Wrapping that up, the benefits of RAID alone can be easily overstated. I'm more inclined to asset that the likely sources of failure will be elsewhere - I've had windows service packs make machines unusable!

All that said, I would encourage you to build a RAID based system - someone should - so that we can all compare notes on the problems we've had in a couple of years time

I'm hoping you start out with three drives to see how you feel about adding a forth drive to the array without having a backup

The #1 reason why I didn't want to go with RAID was because of HEAT and NOISE (fans to cool the heat, and the drives themselves). The more drives the more heat (say 10watts each). Moreover the more drives, the more noise. I know it's possible to run raid5 with less than 5 drives, but as I needed less than 800Gb I figured two 400's better than 5x200 in raid. My mistrust of cheap raid array controllers would have pushed me down the software raid path. I already have 5 drives in another "server", so I know what cooling that sucker takes, and the resultant noise

I also really thought hard about which kind of box to buy: you mention a dell server, but I'm almost certain that you wouldn't want one of those at home because of the noise. My dual processor 3GHz P4 with nVidia FX2000 sounds like a jet artcraft at times (in the office) and that is merely a workstation.

Even, home machines make far too much noise for 24x7 operation - and I'm lucky enough to have a spare room to put one in. I worked pretty hard to get the other server I have to run quietly so that I wouldn't be able to hear it at night (homebrew with Antec Sonata case and extra quiet fans) even though it's in another room.

Another thought I had was actually spinning down the drives when they are not in use, or just keeping the single active drive spun up. This would certainly reduce the noise and power etc. However, I'm not entirely sure that that is a good idea as the failure rates for the drives might change with repeated starting and stopping. (Any data lAmBoY?)