[PVE-User] Shared storage on NAS speed - LVM(over iSCSI) vs NFS

Mikhail m at plus-plus.su
Wed Jul 19 11:32:05 CEST 2017


Thanks for your responses.
The issue appears to be somewhere beyond iSCSI.
I just tried to do some "dd" tests locally on the storage server and I'm
getting very low write speeds:

root at storage:/root# dd if=/dev/vg0/isoimages of=isoimages.vg0
62914560+0 records in
62914560+0 records out
32212254720 bytes (32 GB) copied, 945.573 s, 34.1 MB/s
root at storage:/root#

(/dev/vg0/isoimages is local LV to the storage server)

So will have to find out what's the problem or bottleneck somewhere else.
Load average on storage server is 4.0-5.0 for the following CPU

according to lscpu output:
Model name:            Intel(R) Xeon(R) CPU E3-1230 v5 @ 3.40GHz
Stepping:              3
CPU MHz:               800.000
CPU max MHz:           3401.0000
CPU min MHz:           800.0000

Could this be due to low (800.000 MHz) CPU frequency?


On 07/19/2017 10:03 AM, Eneko Lacunza wrote:
> El 19/07/17 a las 08:41, Dietmar Maurer escribió:
>>> So I cannot figure out why LVM-over-iSCSI is so slow.
>> I guess your benchmark is simply wrong. You are testing the
>> local cache, because you do not sync the data back to the storage.
> Really, 2.7GB/s for 4x4TB disks in RAID10 seems totally unreasonable (I
> guess they're not SSD drives...)
> I think that in the best conditions that could give about 200-250MB/s
> max, totally sequential writes, etc.
> Don't know why iSCSI is so slow, have you checked CPU usage on both sides?
> Anyhow your test copy is too small, use a file that at least is double
> the available RAM on storage server, or otherwise force sync.
> Cheers
> Eneko

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