XOA - local SR continous replication very slow

Computer Hardware & Server Infrastructure Builds
1

Hi forum,
hi Tom,

first of all, I appreciate the work you are doing by spreading the xcp-ng word in the world.

I stumbled over your youtube channel quiete fast as I firstly was tinkering with xcp-ng and it helped a lot. Thank you for this!

Now to my “problem”.

I have several xcp-ng servers running and I see on all of them that the local backups are slow as f*.

The local SR configuration is as follows:
2 * 4 TB NVMe in software raid type 1
2 * 8 TB HDDs in software raid type 1

I added the additional 8 TB local SR over the CLI.

Now if I’m doing a local backup job. Contious Repliation and Rolling Snapshot the transfer of the VMs is less than 30 MB/s. Therefoe the backup needs days to complete.

XOA is running on the same machine. I tried giving it 8 CPUs an 16 GB RAM, but this didn’t do the trick. I connected It via the internal managment interface (169.254.0.1).

In comparison I also have an external backup of the same Host running. It is a differen XOA which connects to the server and copys the VMs in a delta backup job. This is completley saturating my 1Gbit. The first full backup needed 9 hours and transfered 2.33 TiB of data, which is quite impressive speed.

I don’t understand why the local backup to local HDDs is so slow. I can’t figure out where the bottleneck is.

Any ideas?

Thank you in advance and greetings from Germany,
Dominik

2

Backups run though the XO instance so if it only has one interface then it can be the source of the slow down, also I think the current SMAPI process is still singe thread so the CPU speed can play a big role in the backups. The new SMAPI V3 is in beta right now which will be a much faster re-write.

Also from a storage design adding large drives to a VM is not ideal

3

Hi Tom,

here also thank you for your fast response.

Is there something I can do about it right now?

The sizes of the VHDs are set now, I can’t change them easily.

A queston here, what do you do in an Windows VM szenario, here it isn’t possible to splitt larger Partitions into multiple disks, like on linux with an LVM, or did I miss here something?

Thank you for your advice.
Dominik

4

As I covered in the storage design video I posted above, I attach the data to VM not the host often using iSCSI.

5

Thank you for your response,

I’ll try that. I thought the “detour” over a VM would slow everything down and ads additional overhead.

Hopefully I can try it tomorrow due its 23:00 here in Germany, I’ll give feedback if I got some results.

Thanks again, have nice sunday,
Dominik