ms 2012 r2 large avhdx files (mdaemon)

Question

Hello.

We use the mdaemon mail system in our company and it works stably.
For backup, the arcserve udp system with the CBT module is used.

Our backup plan uses 15 minute copies and they are very large (15 GB to 30 GB). The backup procedure uses shadow copy along with the creation of checkpoints on the hypervisor. We noticed that after creating a checkpoint, the size of the avhd file is almost always equal to the size of the next copy.

There is an assumption that after merging the сheckpoints, the CBT module sees the changes in the VHD file and, as a result, copies them again in the next backup.

Inside the machine, we measured the speed of writing to disk and do not see these changes. The total amount of data for 15 minutes was no more than 500 MB

Answer 1

Hello 96716983,

Please check the next thread: https://social.technet.microsoft.com/Forums/Lync/en-US/4276aa76-8866-4c21-8e91-947c0faab61e/avhdx-file-growing?forum=winserverhyperv

As explained, it is never recommend to run machines using AVGHD/AVHDX while in production. Everytime that there is a change in the this this will be written to the AVHD file thus increasing the size. Specially in the case of differencing disks, as differencing disk is a virtual disk that is used to store changes made to its parent virtual disk. This means that all the changes made in the disk, will be translated to the AVHD. After some time, if your differencing disk is 75GB, the maximunm amount that the AVHD can have is also 75GB or close.

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