Slow backup of Proxmox VMs

[pcnr]

Good evening everyone, I'm sorry to bother but i'm hitting a wall trying to backup Proxmox VMs
What I've tried:
-HornetSecurity VM Backup with an USB HDD connected as passthrough -> superslow / failing constantly
-Standard Proxmox Backup to an SMB share (same usb HDD configured on OpenMediaVault on a Raspberry Pi 5) -> slow
-Finally i'm trying PBS, but it's still super slow and I don't understand why, if it's in the way backups are done or what. If i try a standard single-file copy to the share it's super fast

I try to paste any useful configuration that I know, let me know if I can add anything and thanks in advance for any suggestion!

-speed in this moment (the VM isn't even 500 GB, most of it is still available)

INFO:   0% (556.0 MiB of 500.0 GiB) in 3s, read: 185.3 MiB/s, write: 141.3 MiB/s
INFO:   1% (8.0 GiB of 500.0 GiB) in 17m 10s, read: 7.4 MiB/s, write: 3.3 MiB/s
INFO:   2% (10.0 GiB of 500.0 GiB) in 24m 6s, read: 5.1 MiB/s, write: 4.5 MiB/s

-on PVE i've setup PBS in Datacenter->Storage with content "Backup"
-PBS is a VM on the same host (I've read about the dedicated hardware, but from what i've seen is not supported on Raspberry (?))
-on PBS i've mounted the OVM share locally, then added it to Datastore
-on OMV I have the disk attached, type EXT4
-PBS version 4.1.0, PVE Version 8.4.14

It's an 8 TB HDD so I don't expect it to be lightning fast, but still 5 MiB/s seems really slow to me

Thanks again for the kind support, I'm still testing/trying to learn Proxmox so I'm sorry if I made terrible mistakes

 

[SteveITS]

PBS recommends an SSD or ZFS special device for speed because it has to check if each new chunk exists or not. However if writing is slow using other backup methods that doesn't sound like a PBS issue. Is the destination USB 3? What is the source drive/hardware?

 

[pcnr]

PBS recommends an SSD or ZFS special device for speed because it has to check if each new chunk exists or not. However if writing is slow using other backup methods that doesn't sound like a PBS issue. Is the destination USB 3? What is the source drive/hardware?

Hi Steve, thanks for your reply
PBS is on an HDD, the VM i tried to backup is on a SSD
The destination is an HDD connected via USB 3
I'd like to understand if the issue is a problem or a misconfiguration of the Proxmox host, or if the problem is the destination disk
Unfortunately I don't have a NAS to test, but I can try a Windows Share or something similar on a PC

 

[powersupport]

Hi,

This speed is normal for your setup.

Backups are slow because:

• The backup system is running inside a virtual machine
• The disk is a USB hard drive
• The storage is going through another device (Raspberry Pi)

Backup software does more work than a normal file copy, so even if copying a file feels fast, backups can still be slow.

With an external USB hard drive, speeds around 5–10 MB/s are expected.

Nothing is broken — it’s just a limitation of the hardware setup.

 

[pcnr]

Hi,

This speed is normal for your setup.

Backups are slow because:

• The backup system is running inside a virtual machine
• The disk is a USB hard drive
• The storage is going through another device (Raspberry Pi)

Backup software does more work than a normal file copy, so even if copying a file feels fast, backups can still be slow.

With an external USB hard drive, speeds around 5–10 MB/s are expected.

Nothing is broken — it’s just a limitation of the hardware setup.

Hi powersupport, thanks for you reply
Ok, I wanted to understand if I was doing something wrong, thanks for all the informations!