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Volume managers for Linux

I'm going to be putting together our new Linux machines this weekend. I want one of them to have a massive storage space for music and video, enough so that I won't run out of room for quite a while. To accomplish this, I want to use a volume manager to make the OS think that several physical hard drives are actually a single very large drive.

However, I want to be sure that if one of the physical drives kicks the bucket unexpectedly, I won't lose all the data on the entire volume. You'd think this would be a common concern, something they'd put in the FAQs for volume managers. I couldn't find a single mention of this problem on either the LVM or EVMS site, anywhere. However, after searching for a while, I found a mailing-list discussion that addressed it.

It appears that EVMS will smoothly let a bad drive fail without taking out the rest of the volume when you have multiple drives "linked," as they call it. Then you can attempt to mount the failed drive read-only and recover its data. Other discussions seem to indicate that this is not the case with LVM, but I can't find a definitive statement either way.

So I'm going to go with EVMS, probably with xfs or ext3 on top of it, and cross my fingers.

(Someday, multi-terabyte RAID 1/5 systems will be affordable to home users. Then I will be happy.)

Comments

( 11 comments — Leave a comment )
mangofandango
Jan. 16th, 2004 01:25 pm (UTC)
This is going to be one of those posts where people say things like "yeah, no idea what you just said".

Geekface. ;)

markm
Jan. 16th, 2004 01:41 pm (UTC)
RAID-5 (among other configurations) comes free with Solaris 9. You might want to check that out, seeing as how Sun are now completely supporting the x86 platform now. It's what I use, and it's great.

Also, I have no idea what you just said.
rfreebern
Jan. 16th, 2004 03:33 pm (UTC)
rfreebern
Well, I can do RAID in Linux now, without much difficulty. The problem is that to do a mirrored/striped RAID, for maximum data security, I would need pairs of drives, which I haven't got. So I need to think up a solution that I can apply to my system without spending loads more money.
xmurf
Jan. 16th, 2004 03:34 pm (UTC)
Re: rfreebern
No you don't. Linux MD will do any raid it supports on any combination of drives. It does this by breaking the drives up into stripes of different sizes. I've done it, it works well.
rfreebern
Jan. 16th, 2004 04:38 pm (UTC)
Oh, huh. I hadn't realised that, but I guess it makes sense. Now the problem is that if I mirror, I cut my total storage in half, and part of the point of this exercise was to have a lot more storage. Hmm.
ydna
Jan. 16th, 2004 01:56 pm (UTC)
Speaking from experience here, I got scared away from md, lvm, and evms a while back because, in my tests, when I removed a drive (to simulate a failure), the kernel would lock up. I use hardware RAID all the way, baby. I have been very happy with 3ware's Escalade line. I currently use it to drive a four disk RAID-5 that comes out to about 300GB. It's a little more expensive, but not much more. Especially if you don't have the patience for a failure when you have that much data around. Where the hell am I supposed to back that 300GB to exactly? Someday I'll be able to afford a cheap 360GB drive and back things up to that. But by then, I'll probably have bought four of those and have a 1TB RAID that'll fill up in no time. Damn!!
rfreebern
Jan. 16th, 2004 03:36 pm (UTC)
rfreebern
Kernel lockup isn't so much a problem, since these computers will be mainly workstations. If it locks up, I can hard-reset and then try to recover data by hand if need be. I just don't want the rest of the drives to be irrevocably lost if one of them is.

I'd love to set up a hardware RAID, but I've already spent my allotted computer money and can't afford any more right now. In the future, I'd love to have one, but right now I need to make do with what I have.
markm
Jan. 20th, 2004 01:25 pm (UTC)
Re: rfreebern
(don't read this since at this point I'm just evangelising)

Solaris 9 can do RAID without locking up the kernel if a drive is removed. Solaris 9 can raid-5 across as many disks as you've got and want to spare.
brekke
Jan. 16th, 2004 02:08 pm (UTC)
*blinkie*

But can you still draw teenage mutant ninja turtle heads?
rfreebern
Jan. 16th, 2004 03:36 pm (UTC)
Most likely. I haven't tried lately, but they were never all that difficult. :)
_right_as_rain_
Jan. 19th, 2004 10:10 am (UTC)
yo waht the FUCK are you guys talking about
( 11 comments — Leave a comment )

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