Different speed write/read throught iSCSI

[Marian.Veverka]

Hello,

I have the Proxmox 6 connected throught the network (1 switch) to iSCI on Dell Storage. All looks right, but writing is 100x speeder, than reading.
Has anyone meet with it yet?

THX

 

[bbgeek17]

There could be 10s if not hundreds reasons for your experience. You really have to peel layers to get to the simplest possible repro.
For example - use fio/dd directly from the host, without VM. Use netperf between two clients to isolate the storage.
Try different cables/ports, get a network trace to analyze for packet loss and retransmits.

Good luck

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Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[Marian.Veverka]

root@vig-node1:~# dd if=/dev/urandom of=/mnt/test3
^C7335408+0 records in
7335407+0 records out
3755728384 bytes (3.8 GB, 3.5 GiB) copied, 29.2377 s, 128 MB/s

root@vig-node1:/mnt# dd if=/mnt/test3 of=/mnt/test/test4 oflag=direct status=progress
57174528 bytes (57 MB, 55 MiB) copied, 55 s, 1.0 MB/s^C
113569+0 records in
113569+0 records out
58147328 bytes (58 MB, 55 MiB) copied, 55.918 s, 1.0 MB/s
CTRL+C
root@vig-node1:/mnt# dd if=/mnt/test3 of=/mnt/test/test4 status=progress
3623843840 bytes (3.6 GB, 3.4 GiB) copied, 10 s, 362 MB/s
7335407+0 records in
7335407+0 records out
3755728384 bytes (3.8 GB, 3.5 GiB) copied, 77.9442 s, 48.2 MB/s
root@vig-node1:/mnt# dd of=/mnt/test3 if=/mnt/test/test4 status=progress
3744973312 bytes (3.7 GB, 3.5 GiB) copied, 10 s, 374 MB/s
7335407+0 records in
7335407+0 records out
3755728384 bytes (3.8 GB, 3.5 GiB) copied, 10.8221 s, 347 MB/s

/mnt/test/ is mounted iSCSI disk

 

[bbgeek17]

If it were me, I'd try to take storage out of the equation, both local and remote. Direct netperf or iperf between two hosts.

One thing is clear, its not Proxmox/Qemu related. Your "dd" tests are run from a fairly vanilla Ubuntu installation.

---

Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox