Hi Sage, Shrinking is ofcourse always a risky operation, but resizing the blockdev while it is active is not a problem, but i'm not sure if it is even possible when the blockdev is in use. When working with iSCSI i always have to unmount the filesystem and then run: blockdev --rereadpt /dev/sdX to get the new size, i can't run that command when the blockdev is in use. For example, XFS, btrfs and ext4 support online resizing (mostly growing), but still you can't grow the blockdev beneath them when it is on use. When using a LV (Logical Volume) underneath the filesystem you can grow the LV and then online grow the filesystem, but again, you can't grow the PV (Physical Volume) when it is in use. Might be that i'm missing something here, but that is my experience when using iSCSI for the last few years, since iSCSI also gives you block devices, RBD won't be much different. Wido On Tue, 2010-08-10 at 14:07 -0700, Sage Weil wrote: > On Mon, 9 Aug 2010, Yehuda Sadeh Weinraub wrote: > > On Mon, Aug 9, 2010 at 3:38 AM, Wido den Hollander <wido@xxxxxxxxx> wrote: > > > Hi Xiaoguang, > > > > > > I don't have a RBD system running at the moment, so i can't check my > > > commands. > > > > > > But when you have /dev/rbd0, you can remove this device with: > > > > > > echo 0 > /sys/class/rbd/remove > > > > > > There might be a resize option, see: > > > http://tracker.newdream.net/issues/42 > > > > > > echo 0 > /sys/class/rbd/refresh > > > > > > > This will update the list of snapshots, but will not resize a mapped > > device. For doing that you'll need to remove/add the device. > > Also, it is highly unrecommended to alter the image while it is > > mapped, as there is no proper locking and notification mechanism. > > Some file systems (ext3 and btrfs for sure, probably xfs?) can handle > online expansion when the underlying block device grows. Is there > anything preventing us from making the rbd refresh allow bdev expansion at > least? > > I wonder if something like LVM lets you shrink a mounted bdev? > > sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
