without setting
Duration: 10 minutes
Size: 41.71 GiB
Speed: 72.5 MiB/s

with setting
Duration: 10 minutes
Size: 41.71 GiB
Speed: 72.87 MiB/s

CPU usage appears to be about the same.

/opt/xo/xo-server/config.toml

NBD also use encryption by default. You can use it unencrypted by removing the NBD purpose on the network and adding insecure_nbd https://docs.citrix.com/en-us/citrix-hypervisor/developer/changed-block-tracking-guide/enabling-nbd.html#enabling-an-insecure-nbd-connection-for-a-network-notls-mode

Duration: 9 minutes
Size: 41.52 GiB
Speed: 75.26 MiB/s

So didn't really make any meaningful difference (was 80MiB/s previously).

@vincentp If you backup multiple VMs in parallel, does the total speed stays at 80MB/s or does it scales with the number of VM ?

Yes it does.

NBD also use encryption by default. You can use it unencrypted by removing the NBD purpose on the network and adding insecure_nbd https://docs.citrix.com/en-us/citrix-hypervisor/developer/changed-block-tracking-guide/enabling-nbd.html#enabling-an-insecure-nbd-connection-for-a-network-notls-mode

I ran 2 full backups together - netdata and truenas are showed 1.45Gb/s so that's definitely an improvement - although it's using a lot of cpu

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
23882 root      20   0 1022156 101484  20560 S 105.0  1.3  18:08.94 xapi
25349 root      20   0   31884   3872   2660 R  66.0  0.0   0:25.54 tapdisk
10163 root      20   0   32696   4896   2900 R  28.7  0.1   2:25.91 tapdisk

VM1
Duration: 10 minutes
Size: 41.51 GiB
Speed: 67.6 MiB/s

VM2
Duration: 10 minutes
Size: 23.25 GiB
Speed: 39.13 MiB/s

Some other backups are running at the moment, when they are done I will measure VM1 by itself to compare to the earlier one I posted.

Do you have NBD enabled on the network used by XO to backup?

yes.

I will try the insecure nbd - ok without encryption since its a direct connection between the machines

80MiB/s between LA and Sydney is already pretty impressive

No, that's local to sydney - no backups occuring between sites.

Higher the latency, longer the backup, except if we choose bigger blocks, which isn't trivial.

When using NBD, it should be a lot better however since we can have more blocks worked in parallel. I achieved a huge bump with more blocks at the same time.

Also, you can also try XO from the source on a physical machine to check the difference (vs XO in a VM)

There's many many many ways to get faster, what's important is to measure each modification boost, because this might help to identify bottlenecks

NBD also use encryption by default. You can use it unencrypted by removing the NBD purpose on the network and adding insecure_nbd https://docs.citrix.com/en-us/citrix-hypervisor/developer/changed-block-tracking-guide/enabling-nbd.html#enabling-an-insecure-nbd-connection-for-a-network-notls-mode

I have 3 sites, each with a separate XO instance managing them

LA DC

• 2 xcp hosts (dual E5-2620v4)
• no shared storage
• 10G direct connection between hosts

I tried CR between the hosts, and it works well.. once you get past the full backup - but those take 24hrs (800GB vms),
S3 Backup - same experience - backups seem to work well once you get past the full backup - but that sometimes takes longer than 24hrs and runs into the next backup schedule. XO has access to the 10G interface and I confirmed it's using that.

Sydney DC

• single xcp host (dual eypc)
• truenas scale (installed yesterday) - dual 25G direct connections to the xcp

Testing full backups to nfs on truenas over 25G network(NDB Enabled) with the shared option to use multiple files enabled. Also XO is connecting via http to avoid stunnel which was using a huge amount of cpu when I first tried it, and it has access to a 25G interface and I confirmed via netdata that the correct interface is being used for the backups

Small vm test.
Duration: 9 minutes
Size: 41.48 GiB
Speed: 81.03 MiB/s

More testing required but its frustrating that we cannot get better speeds than this - could have saved some money and just used 1G cards in the machines!

HomeLab

• single xcp host
• truenas server to be commissioned this week

just doing disaster recovery backups to 2nd local storage on the machine for now (and just as slow) - will use the truenas once I get it in the rack this week.

The bottleneck with the backups is definitely not the network, even on the homelab machine that backs up to local storage I'm only seeing around 60MiB/s

I don't personally find backups over SMB (10GbE in this case) too slow to be usable by any means, many TB of VMs can be backed up in a single night without issues, but remote stuff is very slow.

I'm curious to hear about your CR experience though, as that is something I'm planning to deploy here soon. Where the hosts on the same subnet and had fast connections or was it a remote host with like IPSec handling the connectivity?

Backup performance on xcp/xo is a major problem - currently battling with this at another site where we just installed a truenas server with dual 25G direct connections between the xcp host and the truenas server (with NDB - and we see < 100MiB/s transfers (nfs share on truenas scale latest) - this time the xcp host is a dual eypc 7543 with all nvme and tons of ram.

This thread did help a bit - top on the host was showing stunnel using a lot of cpu - switching the connection from xo to the server tp be http removed stunnel from the equation but it's still too slow - and I did read somewhere that in the next xcp/xen version http is going away and everything will be https only.

I'm currently researching backups on proxmox to see if they have the same sort of performance issues. I really like xcp and xo but when we end up with backups taking so long that they overlap with the next backup schedule that is not usable.

Would the writeblockconcurrency setting help with merges at all?

Was the > 24hrs mark the entire backup process or just the data transfer process?

If you were using Delta backups and then had the backup retention in the schedule set to 1, it is still honored (even if the schedule itself was disabled), so what might have been happening is that it was merging the delta chain every single time you did a backup which takes a long time.

I did some more testing (nothing with huge VMs yet, but with 4 100GB ish ones) and setting the backup retention to 7 (so it only merges things into the Delta every 7 days) made it so the deltas were much faster to complete, otherwise the backup process would get "stuck" while it's merging the deltas into the full, which is the part that takes the longest from my testing.

Of course, once you hit that 7 retention mark, then every backup from there on out has to merge 1 delta into the full so not sure this is a solution but was just curious.

I'm still doing testing but I think the merge process is going to be the largest issue, so much so that it might actually be faster to NOT use Delta's and instead use full backups and just do them less frequently.

I'm going to do more testing myself here soon to see if I can get things to speed up more, will test NBD.

Also @florent I am not seeing the writeBlockConcurrency option within the config files, is it one that I should add or should it already be there?

@vincentp Did you try activating the NBD option ?

Can you back one VM on a NFS on a separate job to check if it's really reading speed that is slow, or if it's the S3 and CR writer ?

No, I don't have any shared storage at that site so cannot test NFS.

I do have NDB enabled on the direct 10G connection between the two hosts.

Can you back one VM on a NFS on a separate job to check if it's really reading speed that is slow, or if it's the S3 and CR writer ?

For now I'm just going to focus on backing up the data inside the vm's (db, websites etc) as that will be quicker.