On 07/24/2014 06:07 PM, Les Mikesell wrote: > On Thu, Jul 24, 2014 at 7:11 PM, Lists <lists at benjamindsmith.com> wrote: >> I have a large disk full of data that I'd like to upgrade to SW RAID 1 >> with a minimum of downtime. Taking it offline for a day or more to rsync >> all the files over is a non-starter. Since I've mounted SW RAID1 drives >> directly with "mount -t ext3 /dev/sdX" it would seem possible to flip >> the process around, perhaps change the partition type with fdisk or >> parted, and remount as SW RAID1? >> >> I'm not trying to move over the O/S, just a data paritition with LOTS of >> data. So far, Google pounding has resulted in howtos like this one >> that's otherwise quite useful, but has a big "copy all your data over" >> step I'd like to skip: >> >> http://sysadmin.compxtreme.ro/how-to-migrate-a-single-disk-linux-system-to-software-raid1/ >> >> But it would seem to me that a sequence roughly like this should work >> without having to recopy all the files. >> >> 1) umount /var/data; >> 2) parted /dev/sdX >> (change type to fd - Linux RAID auto) >> 3) Set some volume parameters so it's seen as a RAID1 partition >> "Degraded". (parted?) >> 4) ??? Insert mdadm magic here ??? >> 5) Profit! `mount /dev/md1 /var/data` >> >> Wondering if anybody has done anything like this before... >> > Even if I found the magic place to change to make the drive think it > was a raid member, I don't think I would trust getting it right with > my only copy of the data. Note that you don't really have to be > offline for the full duration of an rysnc to copy it. You can add > another drive as a raid with a 'missing' member, mount it somewhere > and rsync with the system live to get most of the data over. Then you > can shut down all the applications that might be changing data for > another rsync pass to pick up any changes - and that one should be > fast. Then move the raid to the real mount point and either (safer) > swap a new disk, keeping the old one as a backup or (more dangerous) > change the partition type on the original and add it into the raid set > and let the data sync up. I would, of course, have backups. And the machine being upgraded is one of several redundant file stores, so the risk is near zero of actual data loss even if it should not work. :) And I've done what you suggest: rsync "online", take apps offline, rsync, swap, and bring it all back up. But the data set in question is about 100 million small files (PDFs) and even an rsync -van takes a day or more, downtime I'd like to avoid. A sibling data store is running LVM2 so the upgrade without downtime is underway, another sibling is using ZFS which breezed right through the upgrade so fast I wasn't sure it had even worked! So... is it possible to convert an EXT4 partition to a RAID1 partition without having to copy the files over?