ISCSI vs iSER vs SRP over Ethernet or InfiniBand

iSER vs SRP over Ethernet or InfiniBand

In brief - iSER on InfiniBand closed the gap with SRP in some point, it is now showing higher performance

SRP

Stands for "SCSI RDMA Protocol", SRP was first published as a standard in 2002. It's very mature and completely stable. Typical usage is connecting head nodes with storage nodes so we can build large (and small) ZFS based clusters (RDMA based SCSI over InfiniBand) . It works beautifully with ZFS since each SRP disk works exactly as if it was plugged directly into the head node. In fact, even better: because the disk is served by a target, we can do SCSI-3 persistent reservations on the disks. Getting it to work on an Ethernet network would be very difficult.

Target support is provided by SCST and LIO on Linux, and COMSTAR on Solaris/illumos based systems. SRP was first published as a standard in 2002. It's very mature and completely stable

iSER

Stands for "iSCSI Extensions for RDMA". It basically extends the iSCSI protocol to include RDMA support. Unlike SRP, you can run it on Ethernet.You can use the same software as IP based iSCSI. You just configure the initiator side to use an iSER interface when performing iSCSI discovery. You don't need to learn anything new. As long as your hardware, initiator and target support iSER, it will work.

Target support is provided by SCST and LIO on Linux, and COMSTAR on Solaris/illumos based systems. The protocol specifications were first published in 2004. Like SRP, it is very mature and completely stable