Re: Software RAID5
Lennart Sorensen [EMAIL PROTECTED] writes: On Tue, Jun 06, 2006 at 09:25:48AM +0200, Goswin von Brederlow wrote: I doubt that is ready yet. But other transformations are, raid5 with n disks to n+1 disks and such. None of those will do filesystem transformations and they don't need to. They just rearange the underlying block device to the new scheme. If the device size changes you have to resize the FS yourself. Rearanging the underlying blocks is a major job, and if interrupted in the middle, leaves a huge mess (unless it cleverly maintains the state of the data somewhere). The filesystem part on top is trivial to deal with afterwards. Afaik it does consitently record all changes in the meta data so after a crash it can just resume where it was. That, and doing it while the disks are mounted, is the point of doing it in kernel after all. On the other hand, moving from raid5 with n disks to raid6 with n+1 disks, ought to be easier, although still not trivial. Actualy no. You have to rearange data blocks across more disks and insert the 2nd parity blocks with no spare space being created. That means you have to realy track every single block move. It might actualy be better to convert to raid5 with n+1 disks moved to the back of the disks with free space at the front and then to raid6 with n+1 disks. When you resize raid5 from n to n+1 disks then you will end up with more space. After the first few (first n blocks are crucial) blocks you have a buffer of unused space between the chunk with n+1 disks and the chunk with only n disks and you can rearange bigger and bigger chunks in one go befor having to sync and note the changes in the superblocks. At that point you can repeadately grow the n+1 disks chunk, setup a mirror target and then shrink the n disks chunk from the begining, which is a fairly easy task. Resizing raids is one of the few places a good hardware raid card seems to have an advantage. Yeah. But we are getting there. :) Len Sorensen MfG Goswin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Dan Serban [EMAIL PROTECTED] writes: Goswin von Brederlow wrote: Recent kernels and mdadm have support for rebuilding a raid now. Better to use that where possible. MfG Goswin To say.. move from RAID1 to RAID6? I wasn't aware, seeing that the number of devices changes, and the filesystem has to be modified. Cool if true. I'll go rtfm. I doubt that is ready yet. But other transformations are, raid5 with n disks to n+1 disks and such. None of those will do filesystem transformations and they don't need to. They just rearange the underlying block device to the new scheme. If the device size changes you have to resize the FS yourself. MfG Goswin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
On Tue, Jun 06, 2006 at 09:25:48AM +0200, Goswin von Brederlow wrote: I doubt that is ready yet. But other transformations are, raid5 with n disks to n+1 disks and such. None of those will do filesystem transformations and they don't need to. They just rearange the underlying block device to the new scheme. If the device size changes you have to resize the FS yourself. Rearanging the underlying blocks is a major job, and if interrupted in the middle, leaves a huge mess (unless it cleverly maintains the state of the data somewhere). The filesystem part on top is trivial to deal with afterwards. On the other hand, moving from raid5 with n disks to raid6 with n+1 disks, ought to be easier, although still not trivial. Resizing raids is one of the few places a good hardware raid card seems to have an advantage. Len Sorensen -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Goswin von Brederlow [EMAIL PROTECTED] writes: I doubt that is ready yet. But other transformations are, raid5 with n disks to n+1 disks and such. None of those will do filesystem transformations and they don't need to. They just rearange the underlying block device to the new scheme. If the device size changes you have to resize the FS yourself. That sounds very promising. I wonder how LVM deals with a grown disk used as PV. Matthias -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
On Tue, Jun 06, 2006 at 09:58:24AM -0400, Matthias Julius wrote: That sounds very promising. I wonder how LVM deals with a grown disk used as PV. Well I don't think I have tried that. I have tried moving all LVM data to other drives, then removing the PV, resizing it, and readding the larger PV, and then adding it back to LVM. I would hope LVM deals with resizing PVs though, but I did not want to risk trying it. Len Sorensen -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Lennart Sorensen [EMAIL PROTECTED] writes: On Tue, Jun 06, 2006 at 09:58:24AM -0400, Matthias Julius wrote: That sounds very promising. I wonder how LVM deals with a grown disk used as PV. Well I don't think I have tried that. I have tried moving all LVM data to other drives, then removing the PV, resizing it, and readding the larger PV, and then adding it back to LVM. Unfortunately my RAID5 is the only volume in my LVM. So it is not really possible here to move the date somewhere else. I would hope LVM deals with resizing PVs though, but I did not want to risk trying it. I would be willing to risk that (since I have a backup). I just would like to know before whether and how LVM is supposed to deal with that. I guess I should go back and RTFM. Matthias -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
I would hope LVM deals with resizing PVs though, but I did not want to risk trying it. I would be willing to risk that (since I have a backup). I just would like to know before whether and how LVM is supposed to deal with that. man pvresize Paul -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Paul Brook [EMAIL PROTECTED] writes: man pvresize Ahh, this is new in testing. I didn't know that since I am running Sarge. And there is no pvresize. Thanks, Matthias -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
On Sun, 28 May 2006 13:00:19 +0200, Jean-Luc Coulon (f5ibh) wrote: Hi, I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances - behaviour in case of a crash Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? Regards Jean-Luc I managed to switch from a 2x200Gb RAID-0 to a 3x200Gb RAID-5 without reinstalling using raidreconf http://unthought.net/raidreconf/ on my AMD64. I'm still amazed it work flawlessly, as latest raidreconf dates from 2001! Obviously I backed-up everything before, but I didn't need used it. Although I ran in a Amd64, I compiled raidreconf as a 32-bit application, since I was afraid it wasn't 64-bit clean. Then it's a matter of writing two raidtabs -- one describing the current raid setup, and another describing the desired setup -- and run raidreconf. José Fonseca -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Jose Fonseca [EMAIL PROTECTED] writes: On Sun, 28 May 2006 13:00:19 +0200, Jean-Luc Coulon (f5ibh) wrote: Hi, I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances - behaviour in case of a crash Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? Regards Jean-Luc I managed to switch from a 2x200Gb RAID-0 to a 3x200Gb RAID-5 without reinstalling using raidreconf http://unthought.net/raidreconf/ on my AMD64. I'm still amazed it work flawlessly, as latest raidreconf dates from 2001! Obviously I backed-up everything before, but I didn't need used it. Although I ran in a Amd64, I compiled raidreconf as a 32-bit application, since I was afraid it wasn't 64-bit clean. Then it's a matter of writing two raidtabs -- one describing the current raid setup, and another describing the desired setup -- and run raidreconf. José Fonseca Recent kernels and mdadm have support for rebuilding a raid now. Better to use that where possible. MfG Goswin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
Goswin von Brederlow wrote: Jose Fonseca [EMAIL PROTECTED] writes: On Sun, 28 May 2006 13:00:19 +0200, Jean-Luc Coulon (f5ibh) wrote: Hi, I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances - behaviour in case of a crash Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? Regards Jean-Luc I managed to switch from a 2x200Gb RAID-0 to a 3x200Gb RAID-5 without reinstalling using raidreconf http://unthought.net/raidreconf/ on my AMD64. I'm still amazed it work flawlessly, as latest raidreconf dates from 2001! Obviously I backed-up everything before, but I didn't need used it. Although I ran in a Amd64, I compiled raidreconf as a 32-bit application, since I was afraid it wasn't 64-bit clean. Then it's a matter of writing two raidtabs -- one describing the current raid setup, and another describing the desired setup -- and run raidreconf. José Fonseca Recent kernels and mdadm have support for rebuilding a raid now. Better to use that where possible. MfG Goswin To say.. move from RAID1 to RAID6? I wasn't aware, seeing that the number of devices changes, and the filesystem has to be modified. Cool if true. I'll go rtfm. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: Software RAID5
On Sun, May 28, 2006 at 01:00:19PM +0200, Jean-Luc Coulon (f5ibh) wrote: I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances - behaviour in case of a crash Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? Well the simplest is backup and start over. The slightly less simple but maybe workable solution is: Break the raid1 by marking one of the disks as faulty, then remove it from the raid1, then setup your raid5 in degraded mode (as in one disk missing), and then when all done and you copied all the data over, delete the old raid1 and add the old disk to the raid5 to bring it up fully. There are many places where you can screw that up, so of course a full backup is worth having. It would be much simpler to just set it up on a new set of disks and copy the data over. How many disks and what size are you planning for the raid5? Len Sorensen -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Software RAID5
Hi, I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances - behaviour in case of a crash Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? Regards Jean-Luc pgpDDYrPlHxVO.pgp Description: PGP signature
Re: Software RAID5
Jean-Luc Coulon (f5ibh) [EMAIL PROTECTED] writes: Hi, I've a system with a software raid1 on 2 sata drive 80 GB I've all my system on LVM on this underlying raid. For performances reasons (video editing), I'm thinking if a RAID5. Is there somebody with some experience with raid5: - performances Slower on write (takes cpu power). Better use a striped lvm on plain disks for temp storage and raid only for the source and final product. You also want PCIe or PCI-X for the disk controler. A simple PCI slot is a serious bottleneck. - behaviour in case of a crash It hangs for a while (up to minutes sometimes) before accepting the disk as dead and then goes on. Or the hardware or disk driver crash and take down the kernel depending on the hardware and luck. Is there an easy process to migrate from raid1 to raid5 without reinstalling everything? degrade the raid1, setup a degraded raid5, copy the FS, kill the raid1, resync the raid5. MfG Goswin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
