Like many shops evaluating
storage virtualisation products, America Online (AOL) needed a
better way of migrating data for tiered storage and during storage
hardware upgrades.
However, after evaluating products, including EMC's Invista,
IBM's San Volume Controller (SVC) and Hitachi Data Systems' (HDS)
Universal Storage Platform (USP) virtualising array, the company
went with an unorthodox choice -- fabric-attached appliances from
YottaYotta typically used for pooling storage between multiple
sites.
AOL is using clusters of YottaYotta's GSX 3000 NetStorage nodes
attached to its
Fibre Channel directors (the company has a mix of Brocade
Communications Systems Inc. and Cisco Systems Inc. switches in 16
different fabrics) in its central datacentre to pool block-based
data storage on 300 terabytes (TB) of its 5.5 petabyte (PB) total
storage area network (San) capacity. It has a mix of disk arrays
that include EMC's DMX and Clariion, HDS' USP and Hewlett-Packard
Co.'s (HP) EVA.
YottaYotta's product is typically used to connect clusters of
servers and storage devices over long distances. The product also
performs some WAN optimisation.
"We will also be looking into using YottaYotta's devices for
offsite replication," according to Dan Pollack, operations
architect for AOL, but that's something the ISP considers a bonus
-- instead, the device is already being put to use in portions of
AOL's production environment for block-level storage virtualisation
in one location.
"We have a highly consolidated data center," Pollack said, which
is good when it comes to many areas of administration but can make
things a tangled web when it comes to any kind of data migration.
In the majority of the San environment right now, the back-end
storage arrays are divided into two tiers, with the high-end DMX
and USP on Tier-1 and midrange Clariion and EVAs on Tier-2.
However, Pollack said, data mobility between tiers is practically
nonexistent because of the number of different servers and
applications attached to each array in the 10,000-port
environment.
"Basically, you pick a tier and you stay there," Pollack said.
"If you need a performance problem solved or you overestimated your
needs, you can move to the other tier, but we don't use it for
lifecycle management."
Hardware upgrade migrations can be a logistical nightmare,
Pollack said. "When you have a couple hundred hosts attached to one
or two arrays, it becomes a significant communications issue where
we discuss the array migration three weeks ahead of time and then
perform it with between 10 and 12 storage, host and application
administrators over a period of a month or more."
YottaYotta versus the competition
Pollack bypassed pooling San storage behind its HDS USP. "The
idea of using an 'edge' device -- whether a storage array or host
-- to do virtualisation to us seems a little out of whack," Pollack
said. "You're adding a bunch of workload where a lot of data
workload is already going to begin with. You need that array to
become the pass-through environment for the storage it's already
fronting."
Pollack also pointed out that the HDS arrays will require
hardware upgrades like any other array, and that USP heads are far
more expensive than the 1U YottaYotta nodes if the company wants to
add in more boxes later.
Because the YottaYotta nodes allow for N-way clustering, Pollack
found the network-based system the most scalable of the products he
evaluated, which also include EMC's Invista and IBM's SVC. Invista
and SVC can be run in high-availability pairs so that code upgrades
don't involve an outage, but Pollack said another appeal of
YottaYotta is the ability to do rolling upgrades while load
balancing across the GSX node clusters, and different nodes within
the same cluster can run at different levels of code. "It's not
all-or-nothing, we can do rolling upgrades across our entire
environment and take things a little more slowly."
Pollack admitted AOL still has its reservations about buying
from a less established vendor. "If we felt we had more time to
wait [for products to develop], we would be more likely to choose a
large incumbent supplier," he said. "But we would rather go with a
generic caching platform that's a little more flexible than a
storage virtualisation appliance that doesn't meet our needs."
The company installed the YottaYotta devices behind a mix of
production and test applications earlier this year. The majority of
the 300 or so terabytes of data currently being run through the GSX
clusters in three of the 16 fabrics belongs to production customer
relationship management (CRM), asset management, logistics and
billing applications.
AOL had to work with YottaYotta in the beginning to match up its
data migration scheme with YottaYotta's management interface and
monitoring tools. The devices are working with storage spread out
over all of the different arrays in the environment, since each of
them is connected to multiple fabrics for consolidation
purposes.
Pollack is gung-ho about the storage virtualisation plans, but
said he will be painstaking in the rollout across all of the
company's storage capacity. Extensive testing in each fabric will
take place this year. AOL doesn't like to "mix and match" fabric
vendors, keeping each fabric either all Cisco or all Brocade
switches and intends to keep the fabrics logically separated, as
well.
"It's possible, if it fits our application, that we could see an
Invista in one of the fabrics at a later date," Pollack said. The
company has purchased the YottaYotta devices it's currently using
and considers itself in an advanced stage of evaluation, but it
won't see full rollout until at least next year.
YottaYotta officials declined to comment for this story, saying
that as a general policy, it does not comment on individual
customer deployments.