Re: Can you IMAGE Mirrored OS Drives?
Alternatives would be to have two such backup devices, and configure them, as andy liebman wrote: I may not have been clear what I was asking. I wanted to know if you can make DISK IMAGES -- for example, with a program like Norton Ghost or Acronis True Image (better) -- of EACH of the two OS drives from a mirrored pair. Then restore Image A to one new disk, Image B to another disk. And then have a new working mirrored pair. May I say belatedly (I've been flat out since July 1) that if I were making a significant number of these clones, I'd write a script so that I could clone one drive, drop it in another machine, and let the script run on the other machine to finish the job. I have no idea how many of these you are doing, but automation is nice to avoid finger checks. -- bill davidsen <[EMAIL PROTECTED]> CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Sat, Aug 19, 2006 at 09:05:39AM +0200, Luca Berra wrote: > please, can we try not to resurrect again the kernel-level autodetection > flamewar on this list. There is no need for a flame war. In some situations one is better, in other situations the other is better. Gabor -- - MTA SZTAKI Computer and Automation Research Institute Hungarian Academy of Sciences - - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Sat, Aug 19, 2006 at 03:13:53AM +0200, Gabor Gombas wrote: but you would have to regenerate the initrd and fight again with lilo :( Or you can just build a kernel with md built-in and use the kernel-level RAID autodetection. In situations like this it is _much_ easier and _much_ more robust than all the initrd-based solutions I have seen. please, can we try not to resurrect again the kernel-level autodetection flamewar on this list. L. -- Luca Berra -- [EMAIL PROTECTED] Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN XAGAINST HTML MAIL / \ - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Wed, Aug 16, 2006 at 06:06:24AM -0400, andy liebman wrote: > There is absolutely NO PROBLEM making images of single disks and > restoring them to new disks (thus, creating clones). And it is very > fast. For an OS drive with about 4 GBs of data, it only takes about 5 > minutes to make the image and 3 to restore it. So, after making the > first set of images, it would in theory take under 10 minutes to restore > a mirrored pair. Be prepared that these times will be much larger if you try to clone RAID5, since by looking at just a single disk the image creator program will not be able to read the file system and identify which parts of the partition contain useful data and which parts are empty. Gabor -- - MTA SZTAKI Computer and Automation Research Institute Hungarian Academy of Sciences - - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Wed, Aug 16, 2006 at 09:38:54AM +0200, Luca Berra wrote: > The only risk is if you ever move one disk from one machine to another. > To work around this you can change the uuid by recreating the array with > mdadm, No need to re-create, --update=uuid should be enough according to the man page. > but you would have to regenerate the initrd and fight again with lilo :( Or you can just build a kernel with md built-in and use the kernel-level RAID autodetection. In situations like this it is _much_ easier and _much_ more robust than all the initrd-based solutions I have seen. Also, if you install lilo to the RAID device instead of the MBR, and install a bog-standard MBR using the install-mbr command on every drive, your life will be easier. Gabor -- - MTA SZTAKI Computer and Automation Research Institute Hungarian Academy of Sciences - - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Wed, 16 Aug 2006, andy liebman wrote: > Thanks Gordon, > > I may not have been clear what I was asking. I wanted to know if you can > make DISK IMAGES -- for example, with a program like Norton Ghost or > Acronis True Image (better) -- of EACH of the two OS drives from a > mirrored pair. Then restore Image A to one new disk, Image B to another > disk. And then have a new working mirrored pair. Right (I think) so at the end of the day, you want N servers each with a pair of mirrored drives in it, or do you want N servers each with one drive in it? I was assuming N servers with a pair of mirrored drives, all setup identically... > There is absolutely NO PROBLEM making images of single disks and > restoring them to new disks (thus, creating clones). And it is very > fast. For an OS drive with about 4 GBs of data, it only takes about 5 > minutes to make the image and 3 to restore it. So, after making the > first set of images, it would in theory take under 10 minutes to restore > a mirrored pair. Imaging a partition or whole drive can be done with 'dd', but the partition/drive needs to be offline or read-only when you do this or you'll miss the filesystem cache and end up copying incorrect data. What you can do is fill the partition (if it's a file system) with zeros; dd if=/dev/zero of=bigfile ; rm bigfile, then feed it through gzip to make the image smaller if desierd. > I'm just trying to find out if there would be any "gotchas" in restoring > mirrored drives. I can't think of any, but you never know. I'm not > worried about hostnames. That's easy to fix. Other than losing data you put in the drives after you made the clone, I don't think so, but I may still be a little confused as to what you are trying to achieve though ... Gordon - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Tue, 15 Aug 2006, andy liebman wrote: -- If I were to create disk images of EACH drive (i.e., /dev/sda and /dev/sdb), could I restore each of those images to NEW drives -- with all of their respective partitions -- and have a working RAIDED OS? I ask because my ultimate goal is to put a RAIDED OS on many systems, and once I get ONE working, it would be nice to clone them the way I already clone SINGLE OS drives. Can you clone RAIDS? Yes. I did this some time back to create half a dozen identical systems. I did it with IDE drives, but I don't see why it won't work with SCSI/SATA. The first thing you need is to make sure the partition tables are identical on both drives. (you probably don't, but it'll be much easier) So I started with my good system, and had a copy of the partition table on hda: # sfdisk -d /dev/hda > ~hda.part Made sure all partitions were insync, then shut it down and remove hdb, and replace it with a new blank disk of the same size. It booted just fine, with all partitions degraded. Put the parittion table on the new blank hdb: # sfdisk /dev/hdb < ~/hda.part then I hot-added each partition. eg: # mdadm --add /dev/md1 /dev/hdb1 and so on. Thanks Gordon, I may not have been clear what I was asking. I wanted to know if you can make DISK IMAGES -- for example, with a program like Norton Ghost or Acronis True Image (better) -- of EACH of the two OS drives from a mirrored pair. Then restore Image A to one new disk, Image B to another disk. And then have a new working mirrored pair. There is absolutely NO PROBLEM making images of single disks and restoring them to new disks (thus, creating clones). And it is very fast. For an OS drive with about 4 GBs of data, it only takes about 5 minutes to make the image and 3 to restore it. So, after making the first set of images, it would in theory take under 10 minutes to restore a mirrored pair. I'm just trying to find out if there would be any "gotchas" in restoring mirrored drives. I can't think of any, but you never know. I'm not worried about hostnames. That's easy to fix. Andy - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Tue, Aug 15, 2006 at 06:55:09PM -0400, andy liebman wrote: I will post my recipe here tomorrow for others to see -- maybe it will help somebody else. I just want to edit a few things to clarify before I post it. Some of the gotchas were were amusing -- like I couldn't run LILO on degraded raid1 arrays, and running "mkinitrd" from within damn, could you open a bug on qa.mandriva.com, so we will remember to fix it? Mandriva 2006 produces gzipped initrd files, but running "mkinitrd" by chrooting in from a LIVE CD produces initrd files that needs cpio to decompress and read it. actually up to kernel 2.6.12-18mdk we defaulted to gzipped cramfs initrd. now the default is initramfs. clone SINGLE OS drives. Can you clone RAIDS? It would mean, of course, you can certainly clone raids. that the UUIDs would be the same on each system. Is that bad? Is there any risk here? The only risk is if you ever move one disk from one machine to another. To work around this you can change the uuid by recreating the array with mdadm, but you would have to regenerate the initrd and fight again with lilo :( -- I know there was a lot of discussion on the list a while back about whether or not to mirror SWAP space. Was there ever any conclusion? It yes, with kernel 2.2 mirroring swap led to deadlocks under memory pressure. but with modern kernels the only issue that would prevent you to mirror swap is masochism. L. -- Luca Berra -- [EMAIL PROTECTED] Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN XAGAINST HTML MAIL / \ - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Can you IMAGE Mirrored OS Drives?
On Tue, 15 Aug 2006, andy liebman wrote: > -- If I were to create disk images of EACH drive (i.e., /dev/sda and > /dev/sdb), could I restore each of those images to NEW drives -- with > all of their respective partitions -- and have a working RAIDED OS? I > ask because my ultimate goal is to put a RAIDED OS on many systems, and > once I get ONE working, it would be nice to clone them the way I already > clone SINGLE OS drives. Can you clone RAIDS? Yes. I did this some time back to create half a dozen identical systems. I did it with IDE drives, but I don't see why it won't work with SCSI/SATA. The first thing you need is to make sure the partition tables are identical on both drives. (you probably don't, but it'll be much easier) So I started with my good system, and had a copy of the partition table on hda: # sfdisk -d /dev/hda > ~hda.part Made sure all partitions were insync, then shut it down and remove hdb, and replace it with a new blank disk of the same size. It booted just fine, with all partitions degraded. Put the parittion table on the new blank hdb: # sfdisk /dev/hdb < ~/hda.part then I hot-added each partition. eg: # mdadm --add /dev/md1 /dev/hdb1 and so on. And that's it. you have in your hand a working disk to put (as hda) into a new system, so just put in in and repeat the above, then you have 2 working systems. Shut them down and remove the hdb's and you have 2 degraded systems and 2 new masters to repeat the process. It's time consuming, but it will work. One thing you will need to do is change the hostname on each new system you bring up, and IP address (if not by DHCP). > It would mean, of course, > that the UUIDs would be the same on each system. Is that bad? Is there > any risk here? Probably not. > -- I know there was a lot of discussion on the list a while back about > whether or not to mirror SWAP space. Was there ever any conclusion? If you don't mirror (or RAID) swap, and a sector in the swap partition goes faulty, then it's game over, so if you have swap then it must be raided. I've put swap on RAID1/5 and 6. It might be sub-optimal on RAID-5 and 6, but hey ... Gordon - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: Can you IMAGE Mirrored OS Drives?
} } -- I know there was a lot of discussion on the list a while back about } whether or not to mirror SWAP space. Was there ever any conclusion? It } seems to me that mirroring will ensure that if one drive fails, you } don't lose information in virtual memory. My applications rarely if } every use virtual memory anyway so I'm not worried about speed. I want } the ultimate in stabilty for the OS drive. Otherwise, I guess I would } designate swap space on just one drive (but prepare identical partitions } on each for swap). If the first drive failed (/dev/sda -- with the swap } space), /dev/sdb would become the new /dev/sda anyway. And so fstab } would be correct in pointing to /dev/sda. You should mirror swap space! Otherwise you will have an outage if a disk fails. Most places would not accept an outage for a simple disk failure. IMO. Guy } } Sound opinions welcome. } } Thanks, } Andy Liebman } - } To unsubscribe from this list: send the line "unsubscribe linux-raid" in } the body of a message to [EMAIL PROTECTED] } More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
