Planetarion Forums

meglamaniac · 24 Mar 2003, 20:15

Right.
I'm planning to give my power supply a heart attack by buying 2 Seagate 120Gb 7200rpm drives as this machine is going to be what can best be described as a "media server" for a house full of students. I naively thought, back when I bought this motherboard, that "nahh, I'll never need raid", so I'm left in the position of having no IDE channel spaces left.

This leaves 2 choices.
An IDE UDMA133 card (by far the cheaper option) and mounting one of the drives in a folder on the other with NTFS (it makes life many times simpler to only have to share one logical device)
or
A RAID card and doing whatever it is with RAID that makes two drives act as one large one.

As you can probably tell I'm not too well versed in the world of RAID. I'm vaguely aware that there is software and hardware RAID and that the latter costs significantly more, but thats about it.

Is there any reason why I should even consider RAID? Mounting one at a point in the other with NTFS would be a perfectly acceptable and considerably cheaper solution from my point of view, so is it worth deviating from this?

Thanks.

Jester · 24 Mar 2003, 20:38

Quote:

Originally posted by meglamaniac
Is there any reason why I should even consider RAID?

Redundancy.

But why buy 2x120GB just to get 120GB?

Jester

meglamaniac · 24 Mar 2003, 20:44

I was under the impression RAID was capable of linking two physical drives into one logical drive of a size that is the sum of it's physical members. Having said that, my knowledge of RAID (as I said) is fk all.

So is it NTFS mountpoints all the way then?

Coffee · 24 Mar 2003, 22:47

Quote:

Originally posted by meglamaniac

So is it NTFS mountpoints all the way then?
:)

Do it with 2 drives + raid.

Otherwise when you press delete it'll copy the files from one drive to the other to move it to the recycle bin (which takes forever) as its too stupid to use one at the root of the drive (as it thinks its all one). Just a little niggle but a pain in the arse none the less.

With a raid stripe you also get 2x the speed, which will help if it gets multiple accesses simultaneously.

As an afterthought back everything up to CDR/DVDR as hard drives, and especially raid stripes, simply cannot be trusted anymore :(

meglamaniac · 24 Mar 2003, 23:13

I have the recycle bin disabled on all my drives as I never use it.

Is "raid stripes" the term for what I was talking about above then?

meglamaniac · 24 Mar 2003, 23:33

Riggght, after much fiddling about with google I've got as far as understanding the various different RAID modes, and what I want is RAID-0, or (as was previously said) striping.

In that case I think i'm going to be a rotten cheapskate and buy a simple IDE UDM133 expansion card and then use the software RAID that windows provides to stripe the two drives.
From what I can gather, if I go into diskpart and run "convert dynamic" on both the disks, then run "create volume stripe" I should be there.

Fun fun fun...

Luckeh!!!! · 24 Mar 2003, 23:57

Isn't there a risk running RAID-0 that although it essentially gives much better disk performance, file corruptions and the like are likely to be irretrieveable because of the files being split across two HDDs?

Or have I got that totally wrong? :/

meglamaniac · 25 Mar 2003, 00:19

As far as I've read you're partially right (seeing as I'm learning this right now as I go along don't take my word for it).
If a file on an NTFS striped volume is corrupted (say by a power failure while it was being written to) then it stands just as much chance of being fixed as it would on any basic NTFS volume. This is because chkdsk (or whatver other utility you might use) sees it as one disk and works on it as such - it is abstracted from it to an extent.
If, however, one drive FAILS, then yes I'd be up **** creak without a paddle. As I'm talking about storing large files on these disks, every single file is likely to have parts of itself on both disks, so every single file would be lost if a drive failed - the only hope would be to try and coax the drive into being cloned, partially or wholly, onto another one to get some of it back again.

As none of the info I'm storing is critical, and Seagate Barracudas have proven extremely reliable to me so far, it's a risk I'm willing to take.

Now along comes Jester to tell me I'm totally wrong.

wu_trax · 25 Mar 2003, 00:50

Quote:

Originally posted by Luckeh!!!!
Isn't there a risk running RAID-0 that although it essentially gives much better disk performance, file corruptions and the like are likely to be irretrieveable because of the files being split across two HDDs?

Or have I got that totally wrong? :/

no, you are absolutly not wrong. i use a raid and first one of the harddisks broke (which did cost me about 80GB of movies), i replaced it and a few weeks later the other one broke, movies gone again

if you want to use this raid-0 make really sure you got reliable hard disks, and no crappy ibm-60GB-disks

Jester · 25 Mar 2003, 01:07

Quote:

Originally posted by meglamaniac

Now along comes Jester to tell me I'm totally wrong.

You're totally wrong*.

Jester

*I'm lying. However, I'd look for some 'horror' stories to read before leaping into it. A lot of PC hardware knowledge in the 'jungle' comes from empirical evidence, unfortunately no one person can compile enough of it to really 'learn' from it.

PS. Western Digital > Seagate

CjC · 25 Mar 2003, 17:22

Raid 0 provides striping performance (and bigger volumes) but when the drive dies you have to restore all the data to the volume. A costly issue if your server provided web services to paying customers. Raid 1 and up gives you redundancy which means a drive can die but the server will still be operational (Well at reduced capability - particularly with Raid 5) - so your web business will continue.

That said if you are building a server for multiple users but were able to backup the data regularly and were not to bothered about downtime Raid 0 can be quite useful.

Software Raid is OK but the overhead is CPU use. Hardware Raid doesnt need to borrow CPU time and usually has a memory cache for faster file operations.

meglamaniac · 25 Mar 2003, 17:32

I think i'll take the risk and the overhead with software and striping.
The files will simply be accessable by standard microsoft filesharing within the lan, which will be 100Mbit to 7 other people. I would have thought an XP2000 should be able to cope with any overhead, and if I'm playing games i'll just raise the thread priority of the game and they might have to live with jumpy movies for the duration.

Jester · 25 Mar 2003, 19:04

Quote:

Originally posted by meglamaniac
I think i'll take the risk and the overhead with software and striping.
The files will simply be accessable by standard microsoft filesharing within the lan, which will be 100Mbit to 7 other people. I would have thought an XP2000 should be able to cope with any overhead, and if I'm playing games i'll just raise the thread priority of the game and they might have to live with jumpy movies for the duration.

Hm. Why bother? If it's just 8 people, they usually won't all be using full bandwidth at the same time. In which case their harddrives are going to be the bottlenecks. In theory, they're going to max out your HD bandwidth with just two people anyway. My own experience with copying files over a 100mbit network is that it does lag up the PC a bit. (I realize the three preceding sentences are a bit contradictory.)

All in all: I doubt you're going to notice a great increase in speed because it's going to max out almost as quickly. I think you'll notice the CPU usage more. If you distribute the data on the two HDs 'intelligently' you can get reap the same rewards without quite as much performance (or economic) hit.

Just my .02 bullion.

Jester

meglamaniac · 25 Mar 2003, 19:13

Hmm. Choices choices.
Unless my maths is fked (quite likely) a 100Mbit network should be able to transport 12.5Mb a second yes? Given that your average DivX movie has about 0.1 - 0.2Mb of data per second, how are 2 people going to max it out? Or does windows 'grab' the file rather than playing it remotely?

Jester · 25 Mar 2003, 19:34

Quote:

Originally posted by meglamaniac
Hmm. Choices choices.
Unless my maths is fked (quite likely) a 100Mbit network should be able to transport 12.5Mb a second yes? Given that your average DivX movie has about 0.1 - 0.2Mb of data per second, how are 2 people going to max it out? Or does windows 'grab' the file rather than playing it remotely?

To my knowledge, I've never been limited by the network. And yes, if they're just watching a divx then that shouldn't be a problem. I assumed you meant they were going to copy stuff over the network, using the entire bandwidth. It's quite easy to figure out how two people would max out your HD usage by copying at max though ;p

Jester

CjC · 25 Mar 2003, 22:15

Just one consideration. If it is to be a media server I assume that more than one person will need to access streamed media at once? Thats probably where raid is definately an advantage. You might need to think about the memory caching aspect as multiple file access occurs - and possibly how its networked.

I think Win2k datacenter server is built for this - optimized streaming file code. Not sure how well standard server or pro or xp will handle it but hey, its not like your providing for an office network

Miserableman · 26 Mar 2003, 04:46

Going for RAID over a standard disk arrangement is probably not worth the effort if you only have two disks. RAID 0 and RAID 1 are not sexy, not sexy at all :O(

tyriel · 27 Mar 2003, 16:22

i've setup and/or used raid 0,1,4,5

i'd introduce it to improved disk performance (0 - striping), provide resilience (1 - mirror) or both (5)

i'm still not clear what raid 4 does - but we've got some very expensive network attached storage at work that uses it. so there's something to be said for it.

BUT - those implementations are on fast scsi drives, no more than 36GB (i was told by our consulted expert this was due to access times and spin/lag) and with massively expensive Raid controllers.
The adaptec 2120S (which is crap) is listed in latest simply catalog at £300+. By expensive i think im hitting £1k+ (mylex springs to mind)

Software implementations are overly wasteful of CPU usage. IDE raid until recently i considered a gimmick. Your bottleneck isnt hard drive access rates - its network bandwidth and processor/memory overhead.

I'd go with NTFS partition mounting and have 240Gb of space.
Broadband = 5gb+/day. You'll need it for all the porn

CjC · 27 Mar 2003, 16:48

Raid 4 uses a single disk as the parity and the other disks for space, whereas raid 5 spreads parity over all disks in the set (Interleaved).

Raid 4 can give you more space and slightly better performance when a disk pops as parity is simpler to calculate.

Wombat · 28 Mar 2003, 15:31

Quote:

Originally posted by meglamaniac

As none of the info I'm storing is critical, and Seagate Barracudas have proven extremely reliable to me so far, it's a risk I'm willing to take.

oh dear.

Barracudas are notorious for burning out. Hope your cooling systems are up to the job.

meglamaniac · 28 Mar 2003, 16:03

The two i have at the moment do get rather hot, but the case temp never goes over 34C.

Luckeh!!!! · 28 Mar 2003, 16:40

Quote:

Originally posted by Wombat
oh dear.

Barracudas are notorious for burning out. Hope your cooling systems are up to the job.

Explain please.

BesigedB · 28 Mar 2003, 17:10

Quote:

Originally posted by Wombat
oh dear.

Barracudas are notorious for burning out. Hope your cooling systems are up to the job.

IBMs more so