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Asked: 2015-03-13 08:50:21 +0800 CST

What can I do to restore disk performance on slower Ubuntu VM

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I have Ubuntu 12.04 (x86) running under VMware Workstation 10.0.5 on a Windows 7 x64 host. Disk access in this VM is noticeably slow - it takes ages just to start Firefox, for example, and the disk light is on the whole time. hdparm -tT confirms this:

/dev/sda:
 Timing cached reads:   18100 MB in  1.99 seconds = 9073.75 MB/sec
 Timing buffered disk reads:  42 MB in  3.54 seconds =  11.85 MB/sec

However, I have 2 other VMs on the same host partition (Ubuntu 11.04 and 14.04) and they're both OK:

/dev/sda:
 Timing cached reads:   17388 MB in  2.00 seconds = 8703.76 MB/sec
 Timing buffered disk reads: 210 MB in  3.07 seconds =  68.37 MB/sec

/dev/sda:
 Timing cached reads:   17012 MB in  2.00 seconds = 8511.87 MB/sec
 Timing buffered disk reads: 282 MB in  3.01 seconds =  93.63 MB/sec

The big difference is that the slow machine has been used a lot over time and had a lot of stuff installed, so the virtual disk is 32GB (vs 4GB and 6GB for the other VMs). What can I do to restore disk performance? I tried the VMware De-fragment and Compact commands that they didn't help. The file system is ext4 in all 3 cases.

performance

1 Answers

  1. I ended up creating a new virtual disk in VMware and manually copying the data across. It worked - the machine is now noticeably faster and hdparm reports:

    /dev/sda:
 Timing cached reads:   18598 MB in  1.99 seconds = 9322.95 MB/sec
 Timing buffered disk reads: 394 MB in  3.00 seconds = 131.31 MB/sec

    The steps were:

    1. Shut down the machine.
    2. Add a new virtual disk device (sdb).
    3. Boot from an Ubuntu LiveCD.
    4. Partition the new disk (I had only 1 partition).
    5. mount both old and new partitions
    6. copy data using cp -ax /mnt/sda1 /mnt/sdb1
    7. Shut down
    8. Remove the old disk and change the new one to node SCSI 0:0, so it becomes "sda".
    9. Boot from the Ubuntu LiveCD again and fix grub using the "via chroot" method
    10. Edit /etc/fstab, which referred to the old partition by UUIDs to use /dev/sda1 (or I could have used the new UUID)
    11. Reboot from the new disk and enjoy a faster VM!
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