On 2/3/06, Ed Wilts <ewilts at ewilts.org> wrote: > > On Fri, Feb 03, 2006 at 07:21:33AM -0600, Steve Swantz wrote: > > On 2/2/06, Josh Trutwin <josh at trutwins.homeip.net> wrote: > > > > > > Any thoughts on this issue? I had assumed that putting swap in the > > > RAID and having one partition (say /dev/md2) as the swap partition was > > > the way to go but some netizens argue that this is a performance > > > problem and that if one drive goes bad it'll still boot ok even though > > > one of the swap partitions is dead. > > > > > > > I'm more interested in the machine staying up (as opposed to just > booting > > up) if one of the swap drives dies, so I put swap on a RAID 1 partition. > My > > server is lightly loaded, and I may not be able to get to it fix it for > > several days at a time, so staying up is most important to me than > absolute > > maximum swap performance. > > There are two issues to worry about here, and I believe you may be > getting incorrect information here. I'm not sure if you're referring to me or to Josh. First, if you swap on a non-mirrored volume and that volume fails, > you'll likely crash. Yes. That's why I have swap on a RAID 1 device. Creating swap files on non-mirrored drives will > allow you to boot but not keep you up in the event of a drive failure. Yes. That's why I have swap on a RAID 1 device. Secondly, it's important to note that swap and normal file system > operations aren't the same thing. If you need to swap and the software > mirror goes away, you may not recover anyway. What I've been told is > that swapping is done at a layer that will not survive a drive failure. > Doing some googling, though, I see that this was an issue in 2002 and it > might actually be stable now. I'm not familiar with that. I did have a test/spare box with / on /dev/md0 and swap on /dev/md1 stay up after a having a problem last month. I got a 'degraded array' warning on md0, and a few days later, a 'degraded array' warning on md1 and the machine stayed up. (The same drive was the problem on both md devices.) I don't know enough to say whether swap on RAID1 is robust or if I got lucky. That machine has very little load and 1GB of memory - it's hard to imagine it using swap much. When I rebooted it, swap (md1) came up mirrored (to my surprise) but / (md0) came up as one drive missing. Just to see if it would work, I did a hot add, it synced, and all was back to normal. And yes, I am watching the sales for a new drive.. Personally, I wouldn't worry about any potential performance problems > when swapping. Swapping sucks anyway. Buy memory :-). There's no > point in having excellent performance if your system is flat down with a > busted swap drive. Amen. Steve -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mailman.mn-linux.org/pipermail/tclug-list/attachments/20060203/d17ca2dd/attachment-0001.htm