Very Slow speed Backing up VM on ZFS

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milocheri

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Sep 1, 2022
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Hello, good afternoon, i have 2 SATA Disks (4TB Each) on a ZFS pool, and 1x500GB Windows VM running there, i setup a remote PBS server, and run a Backup task, however the datatransfer rate for that it is very slow (read: 16.8 MiB/s, write: 16.7 MiB/s), PVE (Dedicated Server at OVH) and PBS (GCP VM) both have 1GB bandwith, what can i do to speed up the datatransfer ?

Thanks!

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UdoB said:
I do not grok exactly what your setup looks like, so... guessing:

If the PBS destination disk is "rotating rust": search for it - it is "slow by design". (See also https://pbs.proxmox.com/docs/installation.html#recommended-server-system-requirements)

What is the "ping"-distance between PVE and PBS? You need high IOPS to operate at a sane speed. A WAN connection reduces this. Disclaimer: my own PBS' are on LAN.
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Hi, i have a dedicated server at ovh, i have 2x480GBSSD in raid1 for the OS, and 2x2TBHDD mirror-0 in ZFS Pool, i think the problem is with the ZFS pool performance, it has only a WS2019 machine, i figure out because i run a backup for a vm running in the ssd disk, and it goes just fine, what can i check to know if the problem is in the ZFS pool ?
 
You must max out you Proxmox BS ZS-Pool, with HDD - Raid10 --> ZFS Raid1 (Mirror1) - Stripe - ZFS Raid1 (Mirror2) and every time with HDD use ZFS special device on SSD SATA or NVMe enterprise rated.
Ex. ZFS Mirror on 2x SSD or more Disks as ZFS special device.

* I setup also as VDEV a ZIL/SLOG on on SSD SATA or NVMe.

* I use also HDDs 4k sector and with 7200 RPM. See Seagate IronWolf Pro NAS CMR.

You must have very mutch IOPS over random 4k read/write!

Ex. for 10 GByte full backup there are 2621440k 4k blocks/ chunks on that drive. With 1k = 1024.
These Blocks must read/ write and veryfied, so that take time.

Proxmox BS says only use SSD Drives for the Backup Server, they have mutch more 4k R/W IOPS.

Your disks my be slow 5600 RPM? and SMR (Shingled Magnetic Recording).
That will be realy bad, then take other and make it right.
 
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