• State Not Answered
  • Locked Locked
  • Replies 1 reply
  • Subscribers 16 subscribers
  • Views 3905 views
  • Users 0 members are here
Options
Related
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

VMWare VM Backups and Disk Space Requirements

dsephton
over 5 years ago

Hi Guys

Could I posisbly ask for clarification around space requirements for VRanger.

I cannot find anything specific on this query.

The setup we have is that we have a VM that has multiple disks, each disk on a seperate Datastore.

The Vranger backup is failing due to not enough space.

Im trying to confirm what space I need and where so I can extend the Datastore space.

However, my query is do I need to have say a given % of free space on each drives Datastore (eg 20% free/DS) or do I need enough space in the location where the VMX file is located to be able to store the entire snapshot before its committed to disk ? (eg say the VM total space (split across different Datastores is 100GB) do I therefore need 100GB available on the DS where the .VMX file is located.)

Any advice appreciated.

thanks

Parents
  • 0 over 5 years ago

    Hello.

    I always thought this question has been answered. But I can't find any relevant post. So here we go again.

    Ranger backup relies on VMware snapshot functionality. Prior the backup itself, we make an API call to create a snapshot on Ranger behalf. Snapshot creates delta files for each virtual Hard Disk. Delta files accumulate changes made to the disk and they have a tendency to grow. Ranger has no idea how much time it will take to complete backup (correspondingly for how long the snapshot will exist), how active OS and applications on Guest are, etc. To play safe we assume that 6GB (default) will suffice to let delta file grow and not to exhaust free space in datastore.

    When backup is done, Ranger makes another API call to remove the snapshot. Changes accumulated in delta files are merged into corresponding parent flat vmdk file. Deltas are deleted and free space reclaimed.

    In some rare cases it is possible to set Minimum space lower than default. There could be a reason for that:

    1. VM is off and delta files won't grow at all.
    2. VM is up but it is pretty static.
    3. Customer takes the risk.

    Next question is a location of delta file itself. I actually lost track of it. VMware changes approach few times. At some point all deltas were stored in the same datastore/dir where vmx file resides. Then they decided that it is better to keep delta in the same dir with the parent flat. I believe they ended up with latter approach and let customers adjust. Per following KB (https://kb.vmware.com/s/article/1002929), "In ESXi 5.0 and later, virtual disk redolog (-delta.vmdk) files for snapshots are placed in the same directory as the parent virtual disk (.vmdk) file." Same article describes procedure to change the location.

    Note. We saw some bad design: datastore is provisioned to hold a single disk with minimum or none free space left. For example, 1TB datastore with a singe disk of little less than 1TB. If delta is configured to be stored in the same datastore/dir, we won't be able to proceed.

    Hope, this answers your questions.
    Andrew

Reply
  • 0 over 5 years ago

    Hello.

    I always thought this question has been answered. But I can't find any relevant post. So here we go again.

    Ranger backup relies on VMware snapshot functionality. Prior the backup itself, we make an API call to create a snapshot on Ranger behalf. Snapshot creates delta files for each virtual Hard Disk. Delta files accumulate changes made to the disk and they have a tendency to grow. Ranger has no idea how much time it will take to complete backup (correspondingly for how long the snapshot will exist), how active OS and applications on Guest are, etc. To play safe we assume that 6GB (default) will suffice to let delta file grow and not to exhaust free space in datastore.

    When backup is done, Ranger makes another API call to remove the snapshot. Changes accumulated in delta files are merged into corresponding parent flat vmdk file. Deltas are deleted and free space reclaimed.

    In some rare cases it is possible to set Minimum space lower than default. There could be a reason for that:

    1. VM is off and delta files won't grow at all.
    2. VM is up but it is pretty static.
    3. Customer takes the risk.

    Next question is a location of delta file itself. I actually lost track of it. VMware changes approach few times. At some point all deltas were stored in the same datastore/dir where vmx file resides. Then they decided that it is better to keep delta in the same dir with the parent flat. I believe they ended up with latter approach and let customers adjust. Per following KB (https://kb.vmware.com/s/article/1002929), "In ESXi 5.0 and later, virtual disk redolog (-delta.vmdk) files for snapshots are placed in the same directory as the parent virtual disk (.vmdk) file." Same article describes procedure to change the location.

    Note. We saw some bad design: datastore is provisioned to hold a single disk with minimum or none free space left. For example, 1TB datastore with a singe disk of little less than 1TB. If delta is configured to be stored in the same datastore/dir, we won't be able to proceed.

    Hope, this answers your questions.
    Andrew

Children
No Data