PBS speed drops after +/- 15%

[NViaene]

Hello,


We have installed a new Backup Server 3.3.0 on an HPE DL380 G9 with 44 CPUs, 64GB of memory, and 80TB SSD storage (2x 512GB RAID1 for PBS - 22x 4TB in RAID6 for backups). The PBS is connected via SFP over 10Gb switches, and all other equipment, such as the PVE nodes and SAN, is connected in the same way to the 10Gb switches.

When we start a backup, we achieve speeds of up to 260 MB/sec, but after 15%, the speed drops to 60 to 30 MB/sec.

This is the only backup running at that time, and it is for a single VM.

What could be the cause of this?


Thank you.

 

[dakralex]

Welcome to the Proxmox forum, NViaene!

How is the storage setup on the PBS instance itself (data store, filesystem)? Are the RAIDs on a hardware, software, filesystem level? Could you provide a benchmark on the PBS directly for the data store where the backups are sent to (e.g. fio; there's some guidance at [0])? Are the VM images on the SAN and the PBS backups written to the local RAID?

On a quick glance, it seems like that there's a bottleneck for the hardware because of the memory size. The drop-off at 15% could be because until then everything was written to RAM (>64GB written) and from then on the hardware controller must work through the not yet persisted backup data.

[0] https://pve.proxmox.com/wiki/Benchmarking_Storage

 

[tcabernoch]

What they said. But shorter.

That 15% is your cache. The speed after that is your real speed.