[PVE-User] Proxmox NFS issue

Muhammad Yousuf Khan sirtcp at gmail.com
Wed Nov 6 19:27:47 CET 2013

>    - for ZIL, in your config, 1-8GB size more than enoug in any case
>    - L2ARC - it needs ram to keep header information in ARC, probably
>    lower l2arc than actual
>       - Example: for ZIL and L2ARC, you should be better with 2 x 60GB
>       SSD:
>          - 2 x 40GB for L2ARC, striped, let's say sdb2 and sdc2 - total
>          80GB
>          - 2 x 5GB for ZIL, in mirror, let's say sdb1 and sdb2 - total
>          5GB (mirror)
>         - you should check your ZFS setup in details (compression, atime,
>    ashift, dedup etc.)
First of i am really thankful for such a  informative and helpful email, as
you have discuss so many points i will have to test it one by  one. however
just a question which is still confusing me.

the status that i have showed in my "rsync" examples. it is almost bumps
around 65MB to 70MB read/write performance. which i think is not bad at all.

so my question is why it is showing me good stats  when i am sending or
receiving data from my storage to Proxmox. why it showing delay only inside

Lets say if "compression , Atime, ashift , dedup etc" all creating problem
in VM then why they are not causing the same problem when copy from proxmox
to OmniOS  or OmniOS to proxmox?

>    -
>       - compression: lz4, atime: off, ashift: 12, dedup: off, blocksize
>       128k
>     - you should check your raw ZFS performance on the nas, be careful,
>    not as simple as sounds
>    - check your cache hit rates (arc, l2arc),
>    - check your iostats under load (zpool iostat -v 1)
>    - read carefully the manual of the chosen ZFS implementation,
>    seriously, great tool, but needs some knowledge
>    - sign up to a zfs specific mailing list to get ZFS specific help
> Network:
>    - check your NFS setup on the ZFS server (sync vs. async)
>    - check your Proxmox nfs client settings, how do you mount
> would you please share me that Where can i tweak nfs client settings in

> Proxmox:
>    - try to use writeback cache
i tried that , didnt helpe

>    - compare raw and qcow2 format performance, choose the better one
> ok i will try this but i know previously i did the test and they both
ended up with the same issue..

VERY NOTICEABLE THING IS. it does not happen all the time, e.g, for 5
seconds my networks graph reach 25MBPS  and continues for 6 to 7 seconds
then again goes down to 0.90 to 0.70% which is tooooo much slow. this shows
a ZIG ZAG graph up and down i dont know why.

on the other hand, when coping from Omni to PVE and PVE to Omni. the
bandwidth stats show 70MBPS and this is very constant till file transfer

>    - install proxmox into a kvm and check its pveperf - good indicator
>    - you can mount nfs manually and setup proxmox to use that point as a
>    simple directory -> you can tune nfs parameters
> In kvm:
>    - try to use safe delete regularly or always (overwrite deleted files
>    with 0)
> In general, if you tune one parameter, it should need change other
> parameters as well, for example if you use qcow2 as image format on the
> proxmox server, the zfs compression should be zle or off.
can you please share any link,  where i can get more information on above


one more question, when we are using NFS for hosting VM, isn't it like we
are sanding and receiving data  via "scp" , "rsycn" does VM hosted on
external box operates very differently?

One more confusing point which i want to share, with same settings i am
hosting a VM in virtualbox and my virtualbox VM some time hangs during
copying big file but it does not low down the graph no matter how big the
file is. mean IO read/writes from Virtualbox are very constant.
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