iSCSI tested faster than ibm virtual SCSI

The linux kernel includes a SCSI target infrastructure since 2.6.20. Most of the code is located in the userspace and supports iSCSI, ibm i/pSeries virtual SCSI and Xen SCSIback.

To work properly it needs a bunch of patches on top of 2.6.21-rc.

After I got it working I did some tests with bonnie. First the target:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
                 2G           32124  17 18063   6           45815   4 324.6   0

Now with the vSCSI initiator:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
                 2G           18513   9 16208   5           34003   3 221.4   0

And the iSCSI initiator:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
                 2G           31631  14 12809   4           39241   5 306.3   1

As this tests was done on one OpenPower machine, all transfers uses DMA between the two systems.

The vscsi case is currently limited to 128KiB per request, maybe this is a problem.