Hardware Reference
In-Depth Information
they generally cost more than comparable Seagate models.
Samsung
(
http://
www.samsung.com
) produces a much narrower range of drives than Seagate
or Western Digital, but the drives Samsung does offer are competitive with
comparable units from Seagate and Western Digital. Like Samsung, the last
member of the Big Four,
Hitachi
(
http://www.hitachi.com
)
, produces a relative-
ly narrow range of models. After being burned by the fiasco several years ago
when Deskstar drives were dropping like proverbial flies, we never installed
another Hitachi drive, so we can't comment on their current quality.
Enterprise- Versus Consumer-Grade Drives
If you peruse the hard drive section of an online vendor's store, you may be puzzled
to find two similar drives from the same manufacturer selling for very different
prices. For example, we just checked NewEgg and found a 1 TB Seagate Barracuda
7200.12 for $75 and a 1 TB Seagate Barracuda ES.2 for $160. The capacities are iden-
tical, as are the rotation rates and cache sizes. So why the huge difference in price?
The 7200.12 is a “consumer-grade” drive and the ES.2 is an “enterprise-grade” drive.
Obviously, the ES.2 must be a better drive, right? Well, it depends on how you define
better. The ES.2 isn't faster or more durable than the 7200.12. The ES.2 does have a
longer warranty—five years versus three—but it really isn't any less likely to fail than
the 7200.12.
The real difference is in the firmware. Consumer-grade drives like the 7200.12
have firmware designed on the assumption that they're the only hard drive in the
computer. Accordingly, their firmware has very aggressive error-recovery routines,
which may cause the drive to time out for anything from a few milliseconds to (in
extreme cases) a minute or more. Enterprise-grade drives like the ES.2 have firmware
designed on the assumption that the drive will be running in a RAID, with parity data
available on other physical drives in the system. Accordingly, the ES.2 has much less
aggressive error-recovery routines, because it can assume it will have help from other
drives in recovering errors.
Basically, then, the consumer-grade drive is much better at recovering errors without
assistance, but is therefore more likely to time out, which is a Very Bad Thing for a
drive that's operating as part of an array. The enterprise-grade drive needs a little
help from its friends to recover from errors, but is therefore very unlikely to time out
during error recovery. In an enterprise RAID setup, having a drive time out is very
nearly as bad as having a drive fail completely, so the higher price of enterprise-
grade drives is well worth paying. For a home or small-office system, including one
with a RAID, we think the consumer-grade drives are the better choice.
Solid-StateDrive(SSD)
Solid-state drives serve the same purpose as hard drives—mass storage—but
are purely electronic devices. Rather than storing data on spinning disk platters,
an SSD stores data in flash memory. All but the least expensive SSDs are faster
than the fastest hard drives—sometimes much faster. (In fact, the fastest SSDs
can saturate a SATA 3.0 Gb/s interface, which is the real reason that motherboard
makers are beginning to introduce models with SATA 6.0 Gb/s ports.)
SSDs are simultaneously reliable and unreliable: reliable in the sense that they
have no moving parts and are much less subject to shock damage than rotat-
ing drives, and unreliable in the sense that SSDs are inherently consumable
