Ok I got your point seems logic, but why is this possible with LVM for example?
You can easily do this with LVM without un-mounting the device. Cheers. On Thu, Jul 19, 2012 at 5:15 PM, Wido den Hollander <w...@widodh.nl> wrote: > Hi, > > > On 19-07-12 16:55, Sébastien Han wrote: >> >> Hi Cephers! >> >> I'm working with rbd mapping. I figured out that the block device size >> of the rbd device is not update while the device is mounted. Here my >> tests: >> > > iirc this is not something RBD specific, but since the device is in use it > can't be re-read by the kernel. > > So when you unmount it the kernel can re-read the header and resize the > device. > > Wido > >> 1. Pick up a device and check his size >> >> # rbd ls >> size >> >> # rbd info test >> rbd image 'test': >> size 10000 MB in 2500 objects >> order 22 (4096 KB objects) >> block_name_prefix: rb.0.6 >> parent: (pool -1) >> >> 2. Map the device >> >> # rbd map --secret /etc/ceph/secret test >> # rbd showmapped >> id pool image snap device >> 1 rbd test - /dev/rbd1 >> >> 3. Put a fs on it and check the block device size >> >> # mkfs.ext4 /dev/rdb1 >> ... >> ... >> >> # fdisk -l /dev/rbd1 >> >> Disk /dev/rbd1: 10.5 GB, 10485760000 bytes >> >> 4. Mount it >> >> # mount /dev/rbd1 /mnt >> # df -h >> /dev/rbd1 9.8G 277M 9.0G 3% /mnt >> >> >> 5. Change the image size >> >> # rbd resize --size 11000 test >> Resizing image: 100% complete...done. >> >> # rbd info test >> rbd image 'test': >> size 11000 MB in 2750 objects >> order 22 (4096 KB objects) >> block_name_prefix: rb.0.6 >> parent: (pool -1) >> >> At this point of time, if you perform the fdisk -l /dev/rbd1, the >> block device size will remain the same. >> >> 6. Unmount the device: >> >> # umount /media >> >> # fdisk -l /dev/rbd1 >> Disk /dev/rbd1: 11.5 GB, 11534336000 bytes >> >> Unmounting the directory did update the block device size. >> >> Of course you can do something really fast like: >> >> # umount /media && mount /dev/rbd1 /media >> >> That will work, it's a valid solution as long as there is no opened >> file. I won't use this trick in production... >> >> I also tried to "mount -o remount" and it didn't work. >> >> 7. Resize the fs (this can be performed while the fs is mounted): >> >> # e2fsck -f /dev/rbd1 >> e2fsck 1.42 (29-Nov-2011) >> Pass 1: Checking inodes, blocks, and sizes >> Pass 2: Checking directory structure >> Pass 3: Checking directory connectivity >> Pass 4: Checking reference counts >> Pass 5: Checking group summary information >> /dev/rbd1: 11/644640 files (0.0% non-contiguous), 77173/2560000 blocks >> >> # resize2fs /dev/rbd1 >> resize2fs 1.42 (29-Nov-2011) >> Resizing the filesystem on /dev/rbd1 to 2816000 (4k) blocks. >> The filesystem on /dev/rbd1 is now 2816000 blocks long. >> >> >> Did I miss something? >> Is this feature coming? >> >> Thank you in advance :) >> -- >> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
