Hello, Am 28.06.2008 um 01:41 Uhr schrieb Neil Brown <neilb@xxxxxxx>: > On Friday June 27, Markus@xxxxxxxxxxxxxxxxx wrote: > > Am Freitag, 27. Juni 2008 08:51 schrieb NeilBrown: > > > From: Chris Webb <chris@xxxxxxxxxxxx> > > > Allow /sys/block/mdX/md/rdY/size to change on running arrays, moving > > > the superblock if necessary for this metadata version. We prevent the > > > available space from shrinking to less than the used size, and allow it > > > to be set to zero to fill all the available space on the underlying > > > device. > > I'm very happy of this new feature. But I'm a little confused how to use > > it correctly. > > Can md now recognize the change by itself and I only have to run mdadm > > --grow? Or have I manually update /sys/block/mdX/md/rdY/size and > > afterwards run mdadm --grow? > No, md does not recognise the change by itself. > Currently you need to update ..../size yourself before using > "mdadm --grow" > This should probably be incorporated into mdadm at some stage, but it > hasn't yet. it's some time ago but today i'm able to test this (because now i have a xen kernel which recognizes size changes). I tested with metadata version 0.9, 1.0 and 1.1 but didn't get it to work. I create a raid1: mdadm --create /dev/md1 --level=1 --raid-disks=2 --metadata=1.0 /dev/xvda1 /dev/xvdb1 Then I change the size of xvda1 and get the following kernel message: [ 3281.905317] Setting capacity to 4194304 [ 3281.905317] xvda1: detected capacity change from 1073741824 to 2147483648 After this i do: echo "0" > /sys/block/md1/md/rd0/size No kernel message so far and cat /sys/block/md1/md/rd0/size still shows 1048570. Then the same for xvdb1. And then I tried to grow md1 in the hope it will somehow detect the new size correct, but i only get a very little grow: [ 3345.133882] md1: detected capacity change from 1073729536 to 1073735680 [ 3345.140087] md: resync of RAID array md1 [ 3345.140098] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [ 3345.140105] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync. [ 3345.140121] md: using 128k window, over a total of 1048570 blocks. [ 3345.140129] md: resuming resync of md1 from checkpoint. [ 3345.140412] md: md1: resync done. [ 3345.160064] RAID1 conf printout: [ 3345.160071] --- wd:2 rd:2 [ 3345.160076] disk 0, wo:0, o:1, dev:xvda1 [ 3345.160081] disk 1, wo:0, o:1, dev:xvdb1 Especially "md1: detected capacity change from 1073729536 to 1073735680" makes me wonder. I also tried to set values to /sys/block/md1/md/rd1/size, but all i got was echo: write error: Invalid argument And the output of /sys/block/md1/md/rd1/size never changes. > > To be on the safe side I'd first lvresize one disk of the raid1, then do > > mdadm --grow to let md update/move the superblock of this disk. And after > > this is successful, lvresize the other disk and do mdadm --grow. So in > > case of a failure i wouldn't loose the whole raid1!? > > Am I correct or am I missing something? > You don't want to "mdadm --grow" until everything has been resized. > First lvresize one disk, then write '0' to the .../size file. > Then do the same for the other disk. > Then "mdadm --grow /dev/mdX --size max". I tried mdadm version 3.0.3 and 3.1.1. Is it possible that something has changed inside mdadm? I used kernel 2.6.32-4-xen-amd64 (debian squeeze). Are am I doing something wrong? Has something changed so i'm on the wrong way? Is there another way to do online grow of an raid1 without full resync? Anyone any ideas? Many thanks in advance. -- greetings eMHa
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