Compellent Technologies has announced version 3.5 of its
StorageCenter SAN software, which will now include WAN optimisation
as well as asynchronous replication features that work like thin
provisioning across the wire. The biggest benefit, according to
users and analysts, is that the features are baked in to the array
software and simplified for the midsized user.
According to Chris Lake, corporate IT manager of Sundt
Construction, the new WAN optimisation features have already saved
him some $40,000 a year, but not on bandwidth -- he chalks up that
cost savings to the fact that the company has been able to dump the
licensing and maintenance on the Double-Take software it was using
to replicate data between its headquarters and another site 120
miles away.
Lake said he has also saved by not having to buy a separate WAN
optimisation or WAFS box for transmitting data over the WAN, though
he said he couldn't pinpoint the exact cost savings as he has not
investigated those products.
Lake said the way Compellent performs replication is also saving
him time in the event of a disaster. Most of the company's servers
are diskless, he said; the company has several "dark boxes" at the
remote site -- Novell servers ready to come to life in the event of
a failure at the primary site. The SQL boot volumes and page file
are kept at the ready on the SAN rather than requiring the
rebuilding of a server at the disaster recovery site in the event
of a failure.
"It would take an experienced Novell engineer 8-12 hours to
rebuild a box from scratch, Lake said. "By booting off the SAN, we
can have the dark box up in 15 minutes."
But, this means that Sundt's disaster recovery plan depends
heavily on the SAN at the disaster recovery site being reasonably
up-to-date in the event of an outage, especially for the SQL data
the company has set to replicate once an hour.
"We estimate that we can get by only if the SQL data is no more
than two hours behind," Lake said. This is where quality of service
comes in, he said -- by being able to tell the system to prioritise
the replication of the SQL data above all others, in order to make
sure it's updated most frequently. Meanwhile, Lake said, he's also
used the StorageCenter SAN version 3.5 WAN throttling feature to
use more bandwidth for backing up less-critical systems like email
and file systems across the WAN during off-peak hours and
weekends.
Finally, Lake said, he appreciates that the replication software
uses web-based GUIs and wizards to guide him through setting
replication schedules and QoS parameters.
The new asynchronous replication feature is something Compellent
has dubbed "thin replication" -- a combination of deduplication
performed before data is sent across the WAN, and another process
based on the array's thin provisioning feature.
As with thin provisioning -- in which space is not allocated for
data until it's actually written -- Compellent's updated software
sends only changed packets over the WAN rather than replicating
volume-to-volume on an identical array at the other end of the
wire. This means it doesn't send empty blocks or require the
preallocation of space on the other end of the wire for data.
"It is very positive to see this kind of replication capability
being baked into storage [software], especially for medium and
small deployments," said Brad O'Neill, senior analyst with the
Taneja Group. "There is a clear trend [among] the emerging systems
suppliers requiring them to bring advanced software features into
their offering right out of the gate -- it's the only way to
[present themselves as] a viable alternative to the big guys."
Compellent is not alone in offering baked-in replication -- its
midrange rival EqualLogic also has the feature, though EqualLogic's
replication software does not include the optimisation piece.
"Replicated data from our arrays can be handled in whatever QoS
class the network…managers decide," wrote Dylan Locsin, public
relations manager for EqualLogic, in an email to SearchStorage.
"This provides a consistent single method for managing QoS in the
network for the entire organization."
The features finding their way into midrange arrays could be a
boon to the right users, according to O'Neill, but these products
will probably only continue to appeal to small or midsized
companies with homogeneous environments. Larger, more complex
environments with a combination of host, network and array-based
replication will probably not find the product useful, he said.