VBoxManage modifyhd --compact my-virtual-drive.vdiPlease note, that you can compact only drives that are registered with VirtualBox Media Manager.
Thursday, November 18, 2010
While working with dynamically expanding virtual drives you might notice that it actually virtual drive takes more space than it actually use by the virtual machine, e.g. you removed a bunch of files, defragmented volume, etc. Here is how you can compact VDI drive:
Wednesday, November 17, 2010
While working with virtual machines you often need to copy an existing virtual machine and go from there, however once you try add it to VirtualBox you will get a message like this:
A hard disk with UUID ... is already registered.In this case what you need is re-generate UUID for the VDI image. Here is how you can do that:
VBoxManage internalcommands setvdiuuid my-virtual-drive.vdiThis way the virtual drive my-virtual-drive.vdi will be assigned a new UUID so it can be registered in VirtualBox Media Manager.
There is easy way to measure your partition performance with dd. Here is how to measure write performance by simply coping a file of length 1 Gb:
deby:~# time dd if=/dev/zero of=file bs=1024 count=1000000 1000000+0 records in 1000000+0 records out 1024000000 bytes (1.0 GB) copied, 13.454 s, 76.1 MB/s real 0m13.696s user 0m0.240s sys 0m5.924sSame way we can read that file back into a memory (/dev/shm):
deby:~# time dd if=file of=/dev/shm/file 2000000+0 records in 2000000+0 records out 1024000000 bytes (1.0 GB) copied, 4.19182 s, 244 MB/s real 0m4.334s user 0m0.592s sys 0m3.740sRead more about dd command here.
Tuesday, November 16, 2010
There is an easy way to find out if your XFS partition needs defragmentation. Here is the command (it is part of package xfsprogs):
deby:~# xfs_db -c frag -r /dev/sda10 actual 2903, ideal 2418, fragmentation factor 16.71%Once you see it is pretty high, e.g. above 40% you would need to issue the following command that defragment the drive:
deby:~# xfs_fsr -v /dev/sda10 /home start inode=0