is ext4 file system thin or thick ?

[jagan]

We are using PVE 3.4 and have connected 8 TB disk. Since ext3 fs limited to 2 TB , we had formatted it with ext4 fs & mounted as directory type storage.

When we try to take backup of 600 GB size VM, we are getting same size of backup file.

So we want to understand whether the ext4 fs is thin / thick provision.

 

[LnxBil]

So we want to understand whether the ext4 fs is thin / thick provision.

ext4 is a filesystem and has nothing to do with provisioning. Virtual disks are provisioned as files on top of the filesystem and there are different options like RAW or QCOW2, which then can be thick and thin provisioned.

When we try to take backup of 600 GB size VM, we are getting same size of backup file.

If you wrote to every block at least once and did not compress your backup, yes, than it can be as big as your virtual machine.

 

[jagan]

ext4 is a filesystem and has nothing to do with provisioning. Virtual disks are provisioned as files on top of the filesystem and there are different options like RAW or QCOW2, which then can be thick and thin provisioned.



If you wrote to every block at least once and did not compress your backup, yes, than it can be as big as your virtual machine.

Thanks.
In directory type storage with ext3 FS I can overprovision the space for VMS. But with ext4 I can't over provision the space like LVm type storage.

 

[LnxBil]

In directory type storage with ext3 FS I can overprovision the space for VMS. But with ext4 I can't over provision the space like LVm type storage.

Yes, if you use QCOW2, you can overprovision, but why would you want to do that?

 

[sseidel]

Of course you can, also with RAW. You will need to enable and use TRIM in your VM and then the backup file will only contain the used blocks.
But PVE 3 is really old, I have no idea whether TRIM is supported.