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iscsi target performance issue

Posted: 2017/12/19 13:36:24
by twistmachine
Hi everybody;

We are currently working on centos 7 with target as iSCSI storage backend for vmware ESXi.
We use the latests stable kernel and we have the latest version of tgt.

PROBLEM : We encouter a performance problem on a blockio storage when vm are using thin provisionned volume.

Our storage server is equipped with 10 Samsung 850 Pro 1to SSD in RAID5 with MDADM, 32Go RAM and 4 ethernet Gigs in MPIO.
All is working perfectly when vm are using thick provisionned volume (400MB/s sequential read), performance is considerably slowed (60MB/s sequential read) when vm is on thin provisionned volume.

We cant find a solution to this, as we dont wants to use fileio because performance are slow without emulation of the write cache and this setting is not recommended in production because of data loss risk.

The same hardware was running smoothly on thin propvisionned volume with SCST on Ubuntu but we encountered Memory out issue, so we decided to rebuild on Centos with tgt for stability and to exclude RAM cache for data integrity reason.

If someone have an idea as we already tested lots of solution without finding one for this thin provisionned VM


Re: iscsi target performance issue

Posted: 2019/09/17 19:46:25
by MrCalvin
Did you ever found a solution?
VM and storage is always a high priority subject :-)