Hi All, We backup our VM's with a custom script based on the https://github.com/oVirt/python-ovirt-engine-sdk4/blob/main/examples/back... example. This works fine, but we start to see scaling issues. On VM's where there are a lot of dirty blocks,

the transfer goes really slow (sometimes only 20MiB/sec).

At the same time we see that ovirt-imageio process sometimes uses 100% CPU

(its single threaded?).

On Mon, Feb 6, 2023 at 10:00 AM Jean-Louis Dupond via Users <users(a)ovirt.org&gt; wrote: > > Hi All, > > We backup our VM's with a custom script based on the > https://github.com/oVirt/python-ovirt-engine-sdk4/blob/main/examples/back... > example. > This works fine, but we start to see scaling issues. > > On VM's where there are a lot of dirty blocks, We need to see the list of extents returned by the server. The easiest way would be to enable debug logs - it will be even slower, but we will see these logs showing all extents: log.debug("Copying %s", ext) log.debug("Zeroing %s", ext) log.debug("Skipping %s", ext) It will also show other info that can help to understand why it is slow. > the transfer goes really > slow (sometimes only 20MiB/sec). Seems much slower than expected > At the same time we see that ovirt-imageio process sometimes uses 100% > CPU This is possible, it shows that you do a lot of requests. > (its single threaded?). It uses thread per connection model. When used with backup_vm.py or other examples using the ovirt_imageio.client it usually use 4 connections per transfer so there will be 4 threads on the server size serving the data. Please share debug log of a slow backup, and info about the backup image storage for example, is this local file system or NFS?