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 :)
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