evms and online capacity upgrade

[dekard]

I'm setting up a raid 5 system as a nas and media box for my house and am planning on using EVMS under Gentoo. Does anyone know if EVMS supports online capacity upgrades or raid level migration?

My plan is to start with 3 x 400g re2's on a sata interface card. I'd love to have the ability to add disks later to increase capacity as I'm sure 754 g's won't be enough long term.

 

[unhappy_mage]

I believe that it does. However, I haven't tested it, despite the fact that I want to do that as well. I'll try a test tonight in a virtual machine and see how it goes.

 

[dekard]

I believe that it does. However, I haven't tested it, despite the fact that I want to do that as well. I'll try a test tonight in a virtual machine and see how it goes.

Excellent! I'm still working on getting my VMware server configured.

 

[unhappy_mage]

Well, I did some other things and forgot about this last night. I'm playing with the VM now; I'll update this post as I go along. I'm working with 4 1GB disks, just for speed's sake. They're all located on the same volume so it's gonna take a while...

Well, it's building at 2 MB/s. That's what I get for keeping them all on the same volume And the machine is remarkably un-responsive. Finish in 4 minutes. Meanwhile I'm going to write a test script that will write sequential packed 4-byte integers over the disk, so I have some reliable test material that I know the format of.

 

[dekard]

Well, I did some other things and forgot about this last night. I'm playing with the VM now; I'll update this post as I go along. I'm working with 4 1GB disks, just for speed's sake. They're all located on the same volume so it's gonna take a while...

Well, it's building at 2 MB/s. That's what I get for keeping them all on the same volume And the machine is remarkably un-responsive. Finish in 4 minutes. Meanwhile I'm going to write a test script that will write sequential packed 4-byte integers over the disk, so I have some reliable test material that I know the format of.

I'm working on building a test array right now.. Got 3 virtual ide drives I'm trying to create.. having some problems getting it to accept a file system, but I'm a noob to evms so I'm probably doing something wrong.

 

[unhappy_mage]

It turns out this probably isn't a good way to get reliable test material, at least in terms of speed:

#! /usr/bin/perl
while (1==1) { print pack('N', $n++); }

It's taking 95+% CPU, and I can't tell how far it is. Probably, writing a series of bytes at once would speed things up. But I think I'm just going to leave it and go to lunch. It should finish within an hour, right? Please?

 

[dekard]

It turns out this probably isn't a good way to get reliable test material, at least in terms of speed:

#! /usr/bin/perl
 while (1==1) { print pack('N', $n++); }

It's taking 95+% CPU, and I can't tell how far it is. Probably, writing a series of bytes at once would speed things up. But I think I'm just going to leave it and go to lunch. It should finish within an hour, right? Please?

lol.. we hope.. I'm off to work. I'll check back in a few hours and let you know what I've got.

 

[unhappy_mage]

Hahaha... I figured it out when I noticed the disk monitor wasn't flashing. So I extracted a few things near the end, and they're all in the proper format. So my guess is when you attempt to write off the end of a disk, it succeeds, and the written data is silently thrown away. Not a great way to do it, perhaps, but I didn't write it Can't blame me for it...

Now working on expanding. God only knows how long that'll take.

Edit: cool, there's a time estimate. It looks pretty accurate so far, too

Edit: Took about a half hour to do the re-striping. Now it's gotta re-sync the whole thing, and it looks like that'll take another half hour.

 

[unhappy_mage]

Re-syncing and data check completed. Everything worked as planned, and testing verified it. Guess it's time to go buy myself some more disks and try it for real.

I wish I had more spindles to play with. I think an hour a GB for this operation is unrealistically high, since all four disk images were on the same physical spindle. Hopefully it doesn't take 300 hours (twelve days!) to re-stripe my 300GB disks. A couple hours I can live with; a couple days not so much.

 

[dekard]

Re-syncing and data check completed. Everything worked as planned, and testing verified it. Guess it's time to go buy myself some more disks and try it for real.

I wish I had more spindles to play with. I think an hour a GB for this operation is unrealistically high, since all four disk images were on the same physical spindle. Hopefully it doesn't take 300 hours (twelve days!) to re-stripe my 300GB disks. A couple hours I can live with; a couple days not so much.

Is there any chance I can get you to jump on msn messanger or some such for a walkthrough tonight? I'm just having a beast of a time getting this to work.