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Can anyone point in the right direction on how to remove SWAP out of a RAID1 configuration on Ubuntu 10.04 server? According to the Ubuntu Advanced installation guide, here, it said to add swap to the raid but I am having some serious performance issues. I would like to remove it from the array and recreate it, with the same size, on the two separate drives. Zero data loss on the other array is a must.

Its a remote computer so I would prefer to do it via command-line if possible.

Here is the output from cat /proc/mdstat

md0 : active raid1 sdb1[1] sda1[0]
19530688 blocks [2/2] [UU]

md1 : active raid1 sdb2[1] sda2[0]
957230016 blocks [2/2] [UU]

Swap is on the md0 device.

Thanks

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thiesdiggity
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  • Which array is your current swap on? – Andrew Oct 13 '11 at 05:50
  • Hey Andrew, swap is on the md0 device. Thx – thiesdiggity Oct 13 '11 at 13:50
  • How much swap are you actually doing? – MikeyB Oct 13 '11 at 15:32
  • Hey Mikey, we aren't actually doing much swap but I am thinking that might be degrading the server performance. The reason I am thinking that is because we have another server that is setup with RAID 1 but swap is not part of the RAID and its performance is excellent. The only differences between the two servers are: processors (both with 2 quad cores, just dif versions) and one is running Ubuntu 9.10 while the other is running 10.04. Do you not think swap in the RAID is the issue? – thiesdiggity Oct 13 '11 at 16:31

2 Answers2

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Assuming you've got swap on /dev/md1, this should work (this is in a root prompt):

# mdadm /dev/md1 --fail /dev/sdb2
# mdadm /dev/md1 --remove /dev/sdb2
# mdadm --zero-superblock /dev/sdb2
# mkswap /dev/sdb2
# echo "/dev/sdb2 none swap sw 0 0" >> /etc/fstab
# swapon /dev/sdb2
# swapoff /dev/md1
# mdadm --stop /dev/md1
# mdadm --zero-superblock /dev/sda2
# mkswap /dev/sda2
# echo "/dev/sda2 none swap sw 0 0" >> /etc/fstab
# swapon /dev/sda2

If you use sudo for these (as you probably should), you'll need to change echo $foo >> $blah to echo $foo | sudo tee -a $blah$.

Andrew
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  • Excellent, that doesn't seem too difficult. Can I do that within a normal boot or do I need to boot via Ubuntu Live CD? Thx. – thiesdiggity Oct 13 '11 at 13:52
  • That's from a normal boot - with a LiveCD you wouldn't need to shuffle the active swaps around, just disassemble the array and convert both components to swap. – Andrew Oct 15 '11 at 04:38
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Meanwhile it depends on the version of kernel you use, LSR RAID-1 can give performance boost when reading from it — due to possible read balancing. Also, making swap not using RAID-1 means you have unstable OS (app hangs/crash) when one of the disks has failed. In other words, it's rather senseless idea.

poige
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