[stgt] ISCSI-SCST performance (with also IET and STGT data)

Bart Van Assche bart.vanassche at gmail.com
Wed Apr 1 22:14:24 CEST 2009

On Mon, Mar 30, 2009 at 7:33 PM, Vladislav Bolkhovitin <vst at vlnb.net> wrote:
> 1. # dd if=/dev/sdX of=/dev/null bs=512K count=2000
>                        ISCSI-SCST      IET             STGT
> NULLIO:                 106             105             103
> FILEIO/CFQ:             82              57              55
> FILEIO/deadline         69              69              67
> BLOCKIO/CFQ             81              28              -
> BLOCKIO/deadline        80              66              -

I have repeated some of these performance tests for iSCSI over IPoIB
(two DDR PCIe 1.0 ConnectX HCA's connected back to back). The results
for the buffered I/O test with a block size of 512K (initiator)
against a file of 1GB residing on a tmpfs filesystem on the target are
as follows:

write-test: iSCSI-SCST 243 MB/s; IET 192 MB/s.
read-test: iSCSI-SCST 291 MB/s; IET 223 MB/s.

And for a block size of 4 KB:

write-test: iSCSI-SCST 43 MB/s; IET 42 MB/s.
read-test: iSCSI-SCST 288 MB/s; IET 221 MB/s.

Or: depending on the test scenario, SCST transfers data between 2% and
30% faster via the iSCSI protocol over this network.

Something that is not relevant for this comparison, but interesting to
know: with the SRP implementation in SCST the maximal read throughput
is 1290 MB/s on the same setup.

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