Snapshot becomes huge.

[dinos007]

Hello,

I am running Suse on a windows xp host system. I have initially declared a virtual disk of 188GB out of 250GBs hard drive. After setting up SUSE I take a snapshot. Then when I try to download 80Gbs of data my snapshot vdk file becomes 44Gb big and crushes my virtual machine cause it takes all the host available space. Is this normal? Why would the snapshot file increase in size since the original vmdk file of 188gigs is almost empty. I would appreciatte any help.

Thanx in advance

Dinos

Message was edited by:

dinos007

Message was edited by:

dinos007

[esiebert7625]

Snapshots can grow up to the size of the original virtual disk. When you take a snapshot the original vmdk file becomes read only and any additional changes are written to the delta (snapshot) files. For every block change on the original disk it is written to the snapshot file instead. So they will grow reapidly if you have lots of disk writes inside your VM. If you downloaded 80GB of data on your VM after you snapshot it this will all be written to the snapshot file instead of the original vmdk file.

Here's some more info...

Snapshots take long time to commit - http://www.vmware.com/community/thread.jspa?threadID=74669

Snapshots take long time to commit - http://www.vmware.com/community/thread.jspa?messageID=584324&#584324

Snapshots take long time to commit - http://www.vmware.com/community/thread.jspa?threadID=73553

Beware the long snapshot - http://www.vmwarez.com/2006/11/beware-long-snapshot.html

Snapshot disk space and growth - http://www.vmware.com/community/thread.jspa?threadID=85409&messageID=649362#649362

What is a snapshot - http://www.petri.co.il/virtual_vmware_snapshot.htm

Fyi…if you find this post helpful, please award points using the Helpful/Correct buttons.

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[continuum]

Next time you create a VM and want to use snapshots - do not preallocated all disk-space in advance.

This makes no sense at all and is a complete waste of space.

Use growing (sparse) disks instead.

Very likely your current snapshot is messed up after running out of space on the host.

To revert to the state you had before taking the snapshot edit the vmx-file and remove the disk. Next re-add the original disk.

You may also want to convert it to a sparse format first - with vmware-vdiskmanager.

[dinos007]

Thanx guys. I only wish that these warnings where mentioned during installation of the virtual disk. I thought that the incremental logging of your state of your hard drive would never exceed a couple of gigs. In fact when I first downloaded the data there was no huge increase on the size of the snapshot. The increase happened when I removed the data and redownloaded them.

Dinos

[dinos007]

So what happens if I remove and redownload the data 5 times? The snapshot should exceed the size of the original virtual disk. Does your virtual disk becomes corrupted?

Dinos

[dinos007]

Hmmm,

I edited the vmx file and added the original drive but I cannot boot it. I get the error message:

"Cannot open Linux-flat.vmdk or one of the snapshot disks it depends on. Reason: The file specified is not a virtual disk."

What I did was I changed

scsi0:0.fileName="SUSE Linux-00002-00003.vmdk" to scsi0:0.fileName="SUSE Linux-flat.vmdk"

Was this the right thing to do?

Thanx

Dinos

[continuum]

It would be very stupid to do so ...

Anyway - deleting files while in a snapshot DOES NOT reduce the size of the snapshot !

If you really need to have heavy disk access with frequent filechanges do not use snapshots.

Just see that you edited your post.

Don't reference the *-flat.vmdk but the file without the extra extension.

In this case "SUSE Linux.vmdk"

[dinos007]

What would be very stupid to do so? There is going to be a lot of data recycling at this virtual server. So I would not be suprised if this happened very soon. Vmware is stupid that keeps entering data to the snapshot file instead of the original. And if you intend to mention the word stupid again, maybe you should not reply at this posting at all.

Thanx

Dinos

[continuum · Accepted solution]

You wanna know what I think is stupid ?

Using a preallocated basedisk - create a snapshot and then have heavy disk-access while writing to this snapshot is stupid. Full stop.

I don't blame you for doing so - the VMware docs are not very helpful in this respect.

So if you need to have VMs with heavy disk access AND in case you want to use snapshots just do NOT use preallocated basedisks - like your VM currently has one - as all advantages of a preallocated disk are wasted because snapshot-files are sparse all the time.

Effectively all your writes go to sparse-disks while the original basedisk has lots of unused - wasted - space.

[dinos007]

Thank you

Dinos