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At our December, 2003 meeting, John Spiers of
LeftHand Networks
discussed next-generation storage area networks based in IP protocols.
John started with an overview of some of the storage management issues
facing administrators today. He showed various charts on storage, data
and computing trends. He claimed that in the future there will be more
seamless bridges between systems and networks (showed diagram of an
InfiniBand network).
The installed base of storage devices is divided into Direct Attached
(70%), Network Attached Storage (NAS - 5%), and Storage Area Networks
(SAN - 25%). For IP SANs, there is a choice between a software initiator
(kernel driver) or a dedicated offload engine on a card (still
expensive). The software initiator may consume a significant percentage
of the CPU (as much as 30% or more depending on the type of application
load), however.
John then described the
LeftHand Networks
solution that includes several
data services and virtualization. Their architecture uses a distributed
systems approach to load balance and provide high availability. Storage
is added a "brick" at a time, with dynamic resizing of existing volumes
when you add storage. They use a Quorum cluster management to eliminate
split brains.
They have a proprietary protocol called Advanced Ethernet Block Storage
(AEBS is TCP/IP based) that enables the asymmetric virtualization. They
keep block maps in the client so that they can vector directly to the
appropriate brick for the needed blocks. They also support standard
iSCSI via a proxy on one of the bricks that acts as a client to the
other bricks using their proprietary protocol. They also use AEBS for
remote replication and remote snapshots. They do over-provisioning of
volumes with soft and hard thresholds for the automatic provisioning.
Their devices use Serial ATA drives, so they only do N-way mirrors (no
RAID parity algorithms) due to the fact that raw storage is cheap. They
currently use an authentication based on an IP addresses today, but are
looking at CHAP (iSCSI) and IPSec for the future. They have an SNMP MIB
for management, and are going to comply with SIM-S standards as well.
They have 1/2 TB and 2 TB bricks and have connected up to 60 at a time
(largest customer uses 32). Denver Health is a big customer of theirs
(EMC Shop) and likes the distributed storage (distributed bricks over
multiple floors) that they can manage as a whole.
They OEM an off the shelf RAID controller and use Linux for their
embedded OS where the clustering, management and fail-over run. They
also OEM an Intel motherboard and the aforementioned Serial ATA Drives.
John then talked about some industry trends such as when iSCSI would be
widely available.
Slides for John's talk are available
(PDF 6MB).
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