Very slow backups

M

mn124700

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Feb 22, 2020
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Good morning all. I just rebuilt my Proxmox server after a hardware failure (bad SSD). I'm up and running again witn Proxmox 7.3-1. I'm running into an issue with the backup function. I started a backup of 5 VMs last night. As of now, 12 hours later, it has still not finished! No errors, but very slow. Initially, it was backing up at about 5-6 MB/sec, but this is now down to about 1-2 MB/s. The "IO Delay" for the node is at about 16%.

My setup is a single node, Proxmox 7.3. The system is installed on an SSD and the VMs are on a separate SSD. The backups are being done to an internal HDD (ext4).

How to I go about diagnosing the problem?

Thanks,
Eric
 
Thanks for the quick response.
No ZFS.
HDD: Western Digital 2TB WD Blue PC Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, 256 MB Cache, 3.5" - WD20EZAZ
SSD: SAMSUNG Electronics 870 EVO 2TB 2.5 Inch SATA III Internal SSD (MZ-77E2T0B/AM)

I've got the HDD configured with Type: Directory and Content: VZDump backup file

Any ideas? Thanks again
Eric
 
backup VM one by one , to check if its VM related.
I recommend first backup during stopped vm, then next hot backup only need to read , then next-next hot backup will use dirty bitmaps of qemu to backup only changed blocks.
 
I don't think it's VM related. In looking at the backup log, all VM backups have been very slow. Never more than 4-5 MB/s. And they've all been in a stopped state, except for the first one.
 
SMR HDD's like your cannot handle a lot of writes for a long time and will become very slow due to the way whole tracks need to be read an rewritten by SMR for each write.
 
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Yuck. They should put a warning label! Maybe I'll swap it for another SSD. Is there any good reason to have an HDD?
 
mn124700 said:
HDD: Western Digital 2TB WD Blue PC Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, 256 MB Cache, 3.5" - WD20EZAZ
Click to expand...
That's a SMR HDD so terrible write performance, even for a HDD.
mn124700 said:
Is there any good reason to have an HDD?
Click to expand...
More capacity for the same price. Won't heavily wear when writing a lot to it (will just slowly wear all time when powered on).
 
mn124700 said:
Yuck. They should put a warning label! Maybe I'll swap it for another SSD. Is there any good reason to have an HDD?
Click to expand...
Please don't replace it with a QLC SSD, they are even slower in the same scenario.

EDIT: Or just stop writing to the drive and let is settle for a day to reorganize itself (it does need to stay on) and try again? CMR HDDs are still larger/cheaper than SSDs.
 
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