ISCSI, the long-awaited internet protocol-based storage standard which is set to make storage area networks far more affordable, has been given the seal of approval by the international engineering taskforce.
ISCSI was approved two weeks ago as a proposed standard — a period in which interoperability is tested — but already vendors have announced iSCSI-compatible products. Network Appliance, for example, will add iSCSI support to two of its arrays and file servers. Other major storage vendors should now follow suit.
Prasad Pammidimukkala, product management director at IP storage vendor Nishan Systems, says two other IP storage standards relating to rival technology fibre channel were also given draft approval earlier this year.
“Both iFCP and FCIP got ratified as proposed standards a couple of weeks prior to the ratification of the iSCSI specification.”
All three will remain as proposed standards for at least six months, Pammidimukkala says.
“That’s the phase where interoperability between different vendors’ products is tested and after that, barring any issues, they’ll become draft standards.”
They’ll be drafts for four months, “and again, barring any issues”, they become fully-fledged official IETF standards, he says.
It may seem a long, drawn-out process, but Pammidimukkala says “these minimum periods are intended to ensure adequate opportunity for community review without severely impacting timeliness.”
The common thread of iSCSI, iFCP and FCIP is the “I” and their premise is the same, sending data between SANs via IP.
The two-fibre channel proposed standards differ in what they allow SAN users to do, he says.
“IFCP works by wrapping fibre data in IP packets and mapping IP addresses to individual fibre channel devices.
“By terminating the fibre channel signalling at the iFCP gateway and carrying the storage traffic over IP networks, iFCP breaks the distance of traditional fibre channel networks, which can extend only 10km.”
On the other hand, FCIP “is a simple tunnelling protocol that interconnects two fibre channel fabrics to form one large fabric. It doesn’t offer the fault isolation capabilities of iFCP”.
IFCP allows “massively scalable SANs and SAN-to-SAN interconnection — fibre channel networks are connected to iFCP gateways, which in turn communicate over a MAN or WAN”.
Although the standards have only recently reached the proposed stage, IP SANs are already in existence and Pammidimukkala says demand has been driven by the organisations’ need to have disaster recovery facilities located much further from headquarters than the 10km conventional fibre channel allows.
“Companies realised, especially after September 11, that their disaster recovery and business continuance sites have to be geographically separated to withstand disasters.
“This distance is beyond what traditional fibre channel can handle and that’s where pre-standard iFCP and FCIP products came in and provided and immediate solution.
“Since both ends of the IP link tend to be the same vendor’s products, standards and interoperability have not been an issue — once the standards are finalised, these products can usually become standards-compliant with just a firmware upgrade.”
Pre-standard iSCSI installations are less common.
“There are a few, where customers have seen the value of IP networks. Typically, in an iSCSI solution, the host bus adaptor vendor is different from the storage vendor and therefore, multi-vendor interoperability is a requirement and having a ratified standard definitely helps vendors feel more comfortable in releasing products.”
Selwyn James, enterprise offerings architect at EDS’ Asia-Pacific hosting services division, says EDS is not presently using iSCSI, but believes the standard as it exists at present “will bring the benefits of SAN technology to smaller, edge devices, as current SAN technology rapidly loses cost effectiveness, with reducing capacity requirements.
“This is particularly true when looking at storage utility implementations and iSCSI will enable a much more cost-effective SAN implementation, where quality of service requirements permit its use.
“ISCSI may also provide advantages in delivering SAN services into secure environments, where current SAN technology is unsuitable.”