Enable compression option -c during ZFS Send

[hcpss-gdelrosario]

This change will allow PVE to utilize ZFS Send -c compression option to speed up intra-cluster migration and replication.

The current implementation does not compress streams which significantly slows down migration on VMs/CTs with large data sets (ie, databases, filestorage ...). For example, if a VM is assigned a 512GB ZFS dataset and is migrated into another host, the ZFS Send will transmit 512GB of data regardless if the VM internally used 1GB of disk space or +500GB of space. Using the -c option, upon migrating the VM, due to compression only used datablocks are sent significantly increasing speed.

Note that even if the underlying ZFS source and destination datasets have the setting compression=on (the default setting in PVE), ZFS Send without the -c option will "unpack" the blocks and send the blocks uncompressed to the receiver.

I've tested this on a production cluster on PVE 8.3.3 with many instances of VMs and CTs with ZFS datasets ranging from 16GB all the way up to 1TB+. Migration and replication works as they did before without any issues.

[Fantu]

Hi, if you didn't see it on the main page:

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