This post is intent for InfiniBand/RDMA/ISER newbies that wishes to understand what is ISER, and what are the advantages to use it.
- What is ISER?
- Link Protocol/Transport Comparison
- Storage Protocol Comparison
- OpenStack Support
- iSCSI/iSER Architecture
- What is RDMA?
- HowTo Configure TGT enabled with iSER Transport for RHEL
- HowTo Configure TGT enabled with iSER Transport for Ubuntu
- HowTo Configure LIO enabled with ISER for RHEL7 Inbox Driver
- HowTo Configure LIO enabled with ISER for Ubuntu 14.04 Inbox driver
- HowTo Configure SCST Block Storage Target Enabled with ISER
- Feature-based Comparison of iSCSI Target implementations
- RFC 7145 - iSCSI Extensions for RDMA
What is ISER?
iSER stands for "iSCSI Extensions for RDMA". It is an extension of the data transfer model of iSCSI, a storage networking standard for TCP/IP. It uses the iSCSI components while taking the advantage of the RDMA protocol suite.
What is the link protocol for ISER?
ISER is an RDMA transport for iSCSI, the link protocol could be either Ethernet or InfiniBand at any supported speed (10,40,56,100Gb/s).
What are the ISER advantages?
- iSER uses the RDMA protocol suite to supply higher bandwidth for block storage transfers (zero time copy behavior). To that fact, it eliminates the TCP/IP processing overhead while preserving the compatibility with iSCSI protocol.
- In addition, it has the lowest latency and lowest CPU utilization. Moreover, it enjoys the stability and benefits of the iSCSI protocol like security, high availability and so on.
- Faster than iSCSI, FC, FCoE and easier to manage than SRP
What are the requirements to deploy iSER?
- Applications that can user SCSI and iSCSI layer
- Network capable of passing RDMA
- Adapter cards that supports RDMA (Ethernet of InfiniBand)
- Ethernet switches (with Flow control or PFC)
- InfiniBand switches
- Target that supports iSER
What storage targets supports iSER?
- Linux targets:
- Linux IO (LIO)
- Linux iSCSI target framework (TGT)
- Generic SCSI target subsystem for Linux (SCST)
- Oracle ZFS, Violin Memory, Zadara Saratoga Speed, HP SL4540 Moonshot server and other tailored storage targets.
- Configuring SAN iSER Targets - Oracle® ZFS Storage Appliance Administration Guide, Release 2013.1.3.0
What are the differences between TGT, LIO and SCST?
|User space||Kernel space (in-tree)||Kernel space (out-of-tree)|
|iSER support since 2008||iSER support since kernel 3.10||iSER support since 2014|
|Linux SCSI target framework (tgt) project||Linux SCSI Target||SCST: A Generic SCSI Target Subsystem for Linux|
Link Protocol/Transport Comparison
Storage Protocol Comparison
|Storage Protocol||iSER (iSCSI RDMA)||iSCSI (TCP)||FC||FCoE||SMB Direct||NFSoRDMA||NVMe over Fabrics|
|Transport (link protocol)||Ethernet (RoCE), InfiniBand||Ethernet||FC||Ethernet||Ethernet (RoCE), InfiniBand||Ethernet (RoCE), InfiniBand||Ethernet (RoCE), InfiniBand|
iSER based on TGT target is inbox in OpenStack since Havana release.
iSER data mover for OpenStack accelerates:
- Storage access
- VM migration
- Data/VM replication
The transport layer iSER and/or iSCSI/TCP are transparent to the user. The configuration is simple.