[Users] [TRD] prl_disk_tool: in-place VM disk expand

[Maxim Perevedentsev]

*1. Feature

*/prl_disk_tool resize --resize_partition /in-place VM disk expand

*2. Description*

the prl_disk_tool utility now can expand VM disks in-place.

/prl_disk_tool resize /worked in-place even before
/prl_disk_tool resize --resize_partition /now expands disk, last 
partition (in case of logical paritition, the extended container as 
well) and its filesystem.

As before, you will need
/libguestfs-winsupport/ for last ntfs partition
/libguestfs-xfs /for last xfs partition
/btrfs-progs /for last btrfs partition


The approximate algorithm is as following (for GPT):
1) part-list -> (start, end); blockdev-getsize64 -> diskEnd; store 
partition attrs
2) create overlay image of size newSize on top of current
3) debug sh 'sgdisk -e /dev/sdaN' (working on libguestfs API)
4) part-del /dev/sda N
5) part-add /dev/sda attrs.type start (blockdev-getsize64 - (diskEnd - end))
6) restore partition attrs
7) stretch filesystem (resize2fs, ntfsresize etc)
8) prl_disk_tool merge --external overlay (qemu-img commit)

For MBR, we avoid step (3) and repeat (4)-(5) for extended partition 
before resizing logical (if needed).


If something goes wrong before (8), we just remove overlay and nothing 
will change to original image.
Overlay is lightweight: for 1GB full disk it used only 6.3Mb of space (I 
think it's affordable).

*3. Products*

Virtuozzo 7

Packages:*
*

  * prl-disk-tool >= 7.0.7
  * libguestfs >= 1.31.7
  * btrfs-progs >= 4.2 (optional)
  * libguestfs-winsupport >= 7.2.1 (optional)
  * libguestfs-xfs (in dependencies)
  * qemu-img >= 1.5.3-86

*4. Testing*

Need to test the following cases:

  * /resize --resize_partition /works for
    ext2/ext3/ext4/ntfs/btrfs/xfs/swap last partitions
  * it works for GPT partitions, preserving partition attributes
  * it works for MBR partitions (primary/extended/logical), preserving
    partition attributes.

*5. Known issues
*

  * only listed filesystems are supported
  * LVM is not supported (working on it)
  * GPT disk GUID is not preserved (it may cause specific OSes to fail -
    need to check which ones)
  * Resizing drops internal snapshots (working on it)

-- 
Your sincerely,
Maxim Perevedentsev





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