Tag Archives: raid

Live migrating Btrfs from RAID 5/6 to RAID 10

5 Replies

Recently it was discovered that the RAID 5/6 implementation in Btrfs is broken, due to the fact that can miscalculate parity (which is rather important in RAID 5 and RAID 6).

So what to do with an existing setup that’s running native Btfs RAID 5/6?

Well, fortunately, this issue doesn’t affect non-parity based RAID levels such as 1 and 0 (and combinations thereof) and it also doesn’t affect a Btrfs filesystem that’s sitting on top of a standard Linux Software RAID (md) device.

So if down-time isn’t a problem, we could re-create the RAID 5/6 array using md and put Btrfs back on top and restore our data… or, thanks to Btrfs itself, we can live migrate it to RAID 10!

Continue reading →

More jackalope than jaunty

10 Replies

We have some IBM x3650 servers at work with Adaptec 8k ServeRAID controller cards and SAS drives.

For the life of me I can’t get Jaunty to boot on the machines. It installs just fine, but the initial reboot fails to find the root device and drops me to an “ash” shell which doesn’t ever actually appear. The keyboard also doesn’t work.

It doesn’t matter what RAID array I have, whether I’m using LVM or a standard partitioning scheme with an msdos partition table.. it just doesn’t work.

I’ve added aacraid and several other modules to the initramfs, still no joy.

Add the fact that the machine takes 10 minutes to boot each time I want to test a small change and it’s one super frustrating situation.

Oh, and 8.04 LTS works just fine.

One bug which appears to be a grub issue that I don’t have, which hasn’t been touched since April. There’s another about being unable to find the root device that also hasn’t received any love.

If anyone has some suggestions (install Debian?), let me know. The reason I’m using Ubuntu is because we have a local mirror and Jaunty because it’s a virtual machine and KVM is the way I want to go.

Update: Ahh, problem resolved and it was my fault. See comments..

“Linux Don’t Need No Stinkin’ ZFS”

1 Reply

Linux Magazine has a pretty nice little article about Btrfs, a new enterprise level file system developed by Oracle which recently entered the Linux kernel.

The article has a comparison with ZFS, Sun’s (well, now Oracle’s) file system which is not Linux compatible, as well as some benchmarks. It’s an interesting, short read. The Btrfs file system does look very, very promising.

-c