According to the InfiniBand Trade Association (IBTA), the
open-standards group charged with drafting the specifications for
the 10/20 Gbps networking protocol,
InfiniBand will be coming soon to a storage
environment near you.
The main reason for the IBTA's high hopes came in the form of an
announcement on 25 September that a specification, known as iSER
(iSCSI Extension for RDMA), has been ratified and will become part
of the InfiniBand specification for connecting InfiniBand networks
to iSCSI storage. RDMA stands for Remote Direct Memory Access,
which allows the network adapter to transfer data directly to or
from application memory, which is what makes InfiniBand so fast.
ISER has also become part of the Linux 2.6.18 kernel and will be
included in new versions of both SUSE and Red Hat Enterprise
Linux.
What this ultimately means for storage users, according to
proponents of iSER, is that iSCSI could soon become the choice over
Fibre Channel (FC) in high-performance
compute environments -- or even discriminating mainstream
enterprise storage shops.
"The perception of iSCSI has been as a low-end, low-performance
protocol," said Asaf Somekh, vice president (VP) of strategic
alliances for Voltaire, a switching company that pioneered a
FC-to-InfiniBand gateway two years ago. (Somekh also sits on the
steering committee for IBTA.) "That's not iSCSI's fault. That's
Ethernet's fault."
According to IBTA, companies, including Silicon Graphics (SGI),
Engenio Information Technologies and FalconStor Software are
currently working on iSER products. Enterprise-focused vendors in
switching and connectivity have also entered the market, at least
nominally, through acquisition -- Cisco Systems by buying Topspin
Communications in 2005 and QLogic with its acquisition of
PathScale in 2006. Also, IBM and LSI Logic's Engenio subsidiary
already offer FC-InfiniBand "hybrid" storage products.
One protocol for all?
The ultimate goal, according to Len Rosenthal, VP of marketing
for QLogic and a marketing representative for IBTA, is to have
InfiniBand become a standard protocol in the enterprise data
center, using technology like Voltaire's gateway and iSER for iSCSI
storage to unite FC, iSCSI and, in some cases, Ethernet under one
umbrella.
Now that it's been ratified by IBTA over other RDMA
specifications, such as Myrinet or Quadrics, iSER will be included
in the OpenFabrics standard, which has just that unification in
mind, Rosenthal said.
"We're hoping to see InfiniBand become a more viable alternative
to both Ethernet and FC across multiple applications," Rosenthal
said.
At the same time, Rosenthal admitted, users aren't just going to
unplug their FC systems. For one thing, FC has been around for more
than a decade now, while questions still remain for some in the
industry as to the reliability of iSCSI storage.
"The big news for now is that there's an alternative, and it's
gaining momentum," Rosenthal said.
So far, traction is slow but steady
For now, according to Somekh, the most immediate benefit of iSER
is that it doesn't interfere with transporting data at the packet
level, as opposed to other iSCSI-to-InfiniBand bridging protocols,
such as IPoIB (IP over InfiniBand).
"Now you can take advantage of the speed of RDMA, but move
things as one file at the megabyte level rather than fragmenting
iSCSI over Ethernet or
FCIP," he said.
So far, the IBTA estimates that traction for InfiniBand has been
confined to high-performance computing environments, with around
500 end-user sites deploying InfiniBand products in clustering
applications. Another limitation on InfiniBand's aspirations to
enter the mainstream data center is that it is currently confined
mostly to Linux operating systems, although Microsoft has announced
its intentions to get into the high-performance computing space,
and as of this past June, announced InfiniBand support in its
Microsoft Cluster Compute Server (CCS) 2003 product.
"Infiniband is one of those promising technologies that is
really exciting, [but] still needs to pass the test of meaningful
customer adoption," said Christopher Baer, an account executive
with storage services firm Broadleaf Services LLC, himself an iSCSI
storage user as well as a storage service provider for EqualLogic
Corp. and Riverbed Technology products.
On the other hand, Baer said, he has seen evidence that iSCSI is
"really taking hold in a big way." Baer cited recent developments
in the industry, including Microsoft's acquisition of iSCSI target
maker String Bean Inc., VMware 's support for iSCSI in ESX 3.0 and
the market penetration of IP SAN products, like EqualLogic's PS
Series arrays.
"For customers that do implement Infiniband, it is smart that
they be given the ability to port to an iSCSI storage array," Baer
said. "In fact, I am sure that these customers would demand that
connectivity between the tiers."
"IfiniBand sort of fell by the wayside for a while, but now it's
back," said Arun Taneja, founder and senior analyst with the Taneja
Group. This is good news, according to Taneja. "Even when it first
came out, InfiniBand was the most complete spec I've ever seen. You
can kick a spec like this in the teeth all you want, but you can't
kill it."
Some in the industry have been working on a standard for RDMA with
IP for years with nothing to show for it yet, Taneja said -- for
now, iSER is filling that gap. "At some point, maybe we'll see it,
but for now people have a job to do -- there are certain HPC
[high-performance computing] applications that thrive on that
functionality."