KVM vm super slow hdd speed on ZFS v4.3 Host

[x86fantini]

Hello, my provider gaved me a dedicated server, a physical supermicro with E3 CPU, 32gb ram, 2 x samsung 512 SSD.

instalation has been made via ISO with zfs as maif filesystem.

i have created a cloudlinux/centos KVM machine and disk performance inside vm is very poor, from 5 to 15mb/s while on host it's 3/400 mb/s.

this is PVEPERF:

root@xxxxxxxx:~# pveperf
CPU BOGOMIPS: 52801.28
REGEX/SECOND: 1843358
HD SIZE: 354.17 GB (rpool/ROOT/pve-1)
FSYNCS/SECOND: 15.60
DNS EXT: 29.95 ms
DNS INT: 50.41 ms (xxxxx.it)

my vm setup is:
cache wriththrough with virtIO
8 cpu with numa (4 x 2)


i have moved a snapshot of this vm to a second identhycal server, not with zfs but with ext4 and lvm. from here, perfromance form inside vm it's crazy fast, 5/600 mb/s..yes cached, but it's 100 times faster

can anyone suggest anything to help?

thank you

 

[spirit]

>>FSYNCS/SECOND: 15.60

What is your ssd model ? (zfs need fast sync write, some consumer ssd are pretty shitty with this)
see this blog for ceph (same apply to zfs journal)
https://www.sebastien-han.fr/blog/2...-if-your-ssd-is-suitable-as-a-journal-device/

If you don't need zfs advanced features, I'll recommand your to stick on lvmthin.

 

[x86fantini]

Strange is, on proxmox host, everything seems so fast.
Ssd are samsung pro, seems solid hdd drives, yes not enterprise but a nice ones.

What are nice values in your opiniom, for FSYNC values?

Any config should i check or anyone with such a behaviour?

Thx

 

[spirit]

What are nice values in your opiniom, for FSYNC values?

I'm around 4000 with a small intel s3500.

 

[x86fantini]

So it's you 4000 vs me 15?? Wow seems incredible.
Ok tomorrow i will ask my isp to look into this

Thank you
S