Passthru RAID is much slower than expected.

[NickH]

I have just added a couple of disks to Proxmox and passed them through to a VM. The VM has configured the disks as RAID1. I am now copying data onto the RAID and I am seeing poor performance, with copying happening at about 500MB/hour. I know on another physical machine that the disks can sustain > 1TB/hour. From Toshiba "Maximum Data Transfer Speed (Sustained)(Typ.) = 268MiB/s" which is 1012GB/h. Is this just the overhead of Proxmox passthrough or is something else going on?

 

[shrdlicka]

That sounds a bit extremely slow. On what kind of hardware are you running this. What are you copying many tine files, or large ones?

 

[NickH]

The server is an HP ML110 Gen9 box (14C 28T) with 72GB RAM. The guest is ClearOS7 (binary compatible with Centos7) with 32GB RAM and 8 cores. The files are mainly 2TB sparse files filled to > 80% with a total used capacity of about 15.5TB. There were 9 sparse files and about ~20 much smaller normal files. I used "cp -rav --sparse=always" and it took over 34h to copy the data.