Warning to all readers using Snapshot CBT based backups

Over the last few days I have become aware of a pretty nasty bug with VMware Snapshot API based backups (Any Image based solutions that is not array based and use change block tracking I will not give names).  This bug has been around for a while but has recently been fixed.   The problem happens when you expand a currently presented drive by 128GB’s or larger.   This expansion causes a bug in the CBT that will make all CBT based backups junk.  You will not be able to restore them.   It’s a major pain in the butt.   What is worse you cannot detect this issue until your restore.  So here is how you create the bug:

  • Expand a currently presented drive 128GB’s or more
  • Do a CBT backup
  • Try to restore that backup or any following backup

You can work around this issue with the following process:

  • Expand a currently presented drive 128GB’s or more
  • Disable CBT
  • Re-enable CBT
  • Do a new full backup

This bug has been around since the 4.1 days and I have never run into it.  I believe this is because I have mostly worked in Linux heavy shops.  We always added a new drive and use logical volume management to expand the mount points thus avoiding this issue.

Please give me some good news

Well today I can this problem is fixed in 5.5 U4 so patch away.  It does not fix machines that are incorrectly backing up just avoids future occurrences.  You can read more about it here.

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