[PVE-User] Slow speeds when KVM guest is on NFS

Brian :: bc at iptel.co
Tue Nov 15 23:22:29 CET 2016


Hi Mikhail

The guest that is running - what type of controller / cache?

Thanks


On Tue, Nov 15, 2016 at 10:05 PM, Mikhail <m at plus-plus.su> wrote:
> On 11/16/2016 12:43 AM, Brian :: wrote:
>> What type of disk controller and what caching mode are you using?
>
> The storage server is built with 4 x 4TB ST4000NM0034 Seagate disks,
> attached to LSI Logic SAS3008 controller. Then there's Debian Jessie
> with software RAID10 using MDADM. This space is given to Proxmox host
> via iSCSI + LVM via 10 gbit ethernet. There's 32GB of RAM in this
> storage server, so almost all this RAM can be used for cache (nothing
> else runs there).
>
> I ran various tests on the storage server locally (created local LV,
> formatted it to EXT4 and ran there various disk-intensive tasks such as
> copying big files, etc). My average write speed to this MDADM raid10 /
> LVM / Ext4 filesystem is about 70-80mb/s. I guess it should be much
> faster then that, but I can't find out where's the bottleneck in this
> setup..
>
> # cat /proc/mdstat
> Personalities : [raid10]
> md0 : active raid10 sda2[0] sdd2[3] sdc2[2] sdb2[1]
>       7811819520 blocks super 1.2 512K chunks 2 near-copies [4/4] [UUUU]
>       bitmap: 11/59 pages [44KB], 65536KB chunk
>
> unused devices: <none>
>
> # pvs
>   PV         VG   Fmt  Attr PSize PFree
>   /dev/md0   vg0  lvm2 a--  7.28t 1.28t
>
> Thanks.
>
>>
>>
>>
>> On Tue, Nov 15, 2016 at 9:36 PM, Mikhail <m at plus-plus.su> wrote:
>>> On 11/16/2016 12:33 AM, Brian :: wrote:
>>>> 90.4 MB/s isn't that far off.
>>>
>>> Hello,
>>>
>>> Yes, but I'm only able to get these results when doing simple "dd" test
>>> directly on Proxmox host machine inside NFS-mounted directory. KVM
>>> guest's filesystem is not getting even 1/4 of that speed when it's disk
>>> resides on the very same NFS (Debian installation from stock ISO takes
>>> ~hour to copy first halt of it's files..)
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