3PAR architecture turns low-cost SATA drives into tier 1 storage

As a result of a
growing trend towards iSCSI at the expense of fibre channel (FC) connection, together
with increasingly high capacity but low cost SATA disks, thin provisioning
pioneer 3PAR has spotted a new marketing opportunity—what it calls ‘Nearline
for Online’ capability.

3PAR has realised
that its wide striping architecture can achieve tier 1 disk storage performance
using the normally tier 2 iSCSI-connected SATA devices. That means the SATA
drives can run critical high performance on-line applications alongside less
real-time functions—and save running costs in several ways.

An important
factor in making this viable now is that SATA drives, which have been in use
for a couple of years, have now demonstrated a high level of reliability
whereas initially this was unproven.

Overall data access
and transfer performance is not dependent on disk rotation speed only. For
instance, in a RAID unit, several platters have their own read-write heads; when
the data is ‘wide-striped’ across multiple units this provides simultaneous
reading of multiple parts of the required data, so ensuring multiplied transfer
speeds. 3PAR writes data wide-striped in this way.

3PAR’s software is
quite happy if there is a mix of 15,000 rpm drives (146GB capacity)
or 10,000 rpm drives (400GB capacity) with FC and 750GB enterprise SATA, both within its InServ
storage server hardware. However, there is some capacity inefficiency in mixing
them in this way.

A major factor in
thin provisioning is that the user does not need to plan capacity beyond
incremental additions of units as the existing drives become full. Pooling all
the capacity within one tier and aggregating it together maximises
percentage utilisation and minimises over-provisioning; separately controlling
‘online’ and ‘nearline’ storage is not as efficient or scalable within traditional arrays as both must
carry spare capacity. With one disk tier this is eliminated.

Raw performance
needs to be proved but 3PAR claims its architecture, with SATA, achieves the
performance that most enterprises need—and more reliably than before to better
achieve service level guarantees. FC lovers may wish to dismiss the
reliability claims for SATA; however, 3PAR’s own architecture in any case helps
ensure against problems.

3PAR’s thin
provisioning design uses “chunklets” of data storage which are only
allocated when new storage space is needed. If a drive fails,
the InServ server needs only to replace these lost chunklets, not the entire failed
drive capacity; its ‘Rapid RAID Rebuild’ capability picks up the data from
associated “raidlets” distributed across drives and builds this into a global
spare chunklet pool—also widely spread—so the effect is very fast recovery
to a safe state without interruption to work.

This architecture
was already present of course; so the announcement is really about the way the
market for SATA has been burgeoning. Still, it is worth highlighting
since thin provisioning and tiered-storage is about saving costs, and this focus takes it further.

According to Craig
Nunes, 3PAR’s VP of worldwide marketing, in the last quarter SATA capacity outsold FC
at the rate of 65% to 35%; the quarter before was around 35/65—so
the trend toward SATA is accelerating. The switch may be less marked
in the larger enterprises who have long-established FC and the necessary staff expertise
to manage it, but there is still a higher server-side FC cost.

SO, despite 3PAR’s
enterprise push, the short-term opportunity is potentially even greater among
small and medium businesses (SMBs). In general these never have had FC and are now
buying iSCSI-SATA in ever larger quantities; but they have capacity and
performance issues which are even greater proportionate to business size. “For
SMB’s why build FC up?” said Nunes; he has a point as long as the need for the
highest-performing disks is now obviated.

Here is how the
benefits stack up: i) Thin provisioning 3PAR-style achieves considerable overall
disk capacity savings over storage virtualised in a standard way (as well as over
others’ recently bolted-on thin provisioning); ii) the thin provisioning
approach also hugely reduces storage capacity planning and management (and
therefore the staff costs to do this); iii) because capacity is more
predictable, smaller, more incremental, purchases can be made, nearer to when the
capacity is needed, a further cost saving; iv) for the disk capacity that is
used there is a lower cost with SATA—so the more disk needed the greater the
saving; v) there are lower energy costs and heat output. Cost-conscious enterprises
should find this proposition attractive.

Of course, saving
on disk storage and its running costs is also a green issue. 3PAR is now operating
a carbon-neutral environmental policy. It complements disk capacity savings
(when a company switches to 3PAR and so saves space), with carbon-offsetting
for the rest. The company estimates a saving of equivalent to 12,000 metrics
tons of CO2 in 2007 and is going for an even bigger figure this year.

A measure of 3PAR’s
thin provisioning success to date is perhaps reflected in its recent IPO plus
ongoing worldwide expansion. At this week’s VMworld Europe event in Cannes, 3PAR is announcing a French storage-focused
systems integrator, Antemeta, as its partner covering France and Luxembourg. It is also trumpeting a
major hardware/software win with the German Freudenberg Group (Eu5bn turnover,
33,000 employees in 53 countries). Since 3PAR virtualises storage and VMware
virtualises servers the two are complementary with little or no overlap.