Hyper-V VHD confusion

[Tricky_Dicky]

Hi,

 

I'm hoping there are some gurus on Hyper-V on here as I'm getting really confused with something.

 

On our SAN I've got a volume of 760Gb for our Sims Data drive. On the host I can see the volume is 760Gb so that's fine. Within that volume I've got 3 files, a Sims-Data.VHD at 520Gb, a Sims-Data_LOTS-OF-NUMBERS.AVHD at 248Gb and then a sims-data-expanding.vhd at 17Gb.

 

Within Hyper-V the hard drive attached as the drive is the Sims_Data_LOTS-OF-NUMBERS.avhd.

 

The virtual machine is showing a Data drive of 496Gb in capactity, but with 370Gb free.

 

What's really cooking my brain, is that the machine paused this morning due to running low on space on the disk.

 

Can anyone shed any light on what's gone wrong here and how I can fix it?

 

Many thanks

[Steve21]

The avhd is a differencing disk (normally happens when backing up etc) that allows data to be written while the backup/replica runs.

 

What "should" happen is when it finishes the backup the software remerges the AVHD into the VHD leaving only that behind.

 

By the sounds of it the AVHD split for a backup but hasn't remerged, and as it grew to a size that VHD + AVHD is bigger than the space you got it broke.

 

What backup/replica software you using?

 

Steve

[DavidYoung]

Hi,

 

AVHD files are checkpoint files. 248GB for a checkpoint is huge, you must have had a checkpoint running on that server for a very long time. In HyperV manager, click on the machine and see what checkpoints are in the second panel. You will need to remove the checkpoint but with that size it will take a long time and probably cause a big performance impact while it is moving all the data back into the VHD file.

[Tricky_Dicky]

We are using Redstor for the backup but we don't take snap shots of the servers, we just back up the database and files for SIMS.

 

Any idea what I can do about this? How reliable and how long should it take to merge them back together?

[DavidYoung]

What does it show in checkpoints?

[MYK-IT]

Looks like you've got snapshots of your SIMS (Hyper-V based) VM Server (either intentionally, or not??? maybe from a previous maintenance etc.?)

 

Within Hyper-V manager when you select your SIMS VM Server, you will also see the snapshot(s) detailed below.

 

Either, house-keep and decide which snapshots you want to keep (if any); then schedule a time where by you can shut-down the SIMS VM Server. By doing so, the various VHDs will be merged (back) into one.

 

EDIT:

snapshots = checkpoints

[Tricky_Dicky]

Hi,

 

AVHD files are checkpoint files. 248GB for a checkpoint is huge, you must have had a checkpoint running on that server for a very long time. In HyperV manager, click on the machine and see what checkpoints are in the second panel. You will need to remove the checkpoint but with that size it will take a long time and probably cause a big performance impact while it is moving all the data back into the VHD file.

 

Hi,

 

I can't see checkpoints anywhere within either the Hyper-V or Cluster manager. Where should I see it?

[Tricky_Dicky]

Ahh, there aren't any snapshots showing in the console..

 

The plot thickens

[MYK-IT]

Are you running Hyper-V 2008?

 

I would still schedule a time where you can shut down the SIMS VM Server; and hopefully you will see a status of 'merging' or similar being shown. This process could take a long time; so factor that (down time) in too.

[Tricky_Dicky]

Hyper-V 2008R2.

 

Ok, will try and get it shut down over a weekend and see how it goes from there.

 

Is it just the VM I would need to shut down or the host as well?

[Homer]

Ooohh I managed to leave a snapshot running on SIMS on ESXi once... that took a looooong time to merge and almost failed

 

Defo shut down over half term and see what happens (I know this is Hyper-V)

[Steve21]

Just the VM, when you turn it off rather than it's normal shutting down message in hyperv it should change to merging (for ages) and then shutdown

 

I'd disagree on waiting though, as you will keep crashing everytime that drive fills up and by the sounds of it it's pretty full unless you could make some space temporary?

 

Steve

[Homer]

Ahh yeah if the datastore is full then defo get on it soon as possible. Snapshot disks can bust the defined size of the VHD so can eat all of the space on that datastore

 

Or bad things will happen™

[fiza]

resurrecting this thread as I seem to have a similar issue.

 

I don't have any snapshots (HyperV). We use Veeam to backup the VMs.

On the Host I only have 18GB left where the VMs are stored. The AVHD files I need to merge are 12GB,14GB, 16GB, 61GB, 71GB, 42GB. Several of the VMs on the host have AVHDs attached to them.

 

Slowly the space on the host is getting used up by these AVHD files. How can I remove them if I don't have any snapshots?

[Steve21]

Normally if they're Veeeam ones just shutting down the VM and waiting will make them merge themselves in. They normally seem to occur if a job gets interrupted etc

 

Steve

[fiza]

Normally if they're Veeeam ones just shutting down the VM and waiting will make them merge themselves in. They normally seem to occur if a job gets interrupted etc

 

Steve

 

I've actually just checked and the VMs that Veeam backs up don't have the AVHDs associated with them. Its 3 others that aren't currently backed up.