Different speed write/read throught iSCSI

M

Marian.Veverka

Member
Jun 3, 2020
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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
 
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

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