All of the benchmarks
in this feature were
completed using
Adaptec’s RAID 31605
controller ( $1,000, adaptec.
com ). In our initial tests,
we found that our EVGA 608i
chipset-based RAID speeds
simply paled in comparison. Thanks
to an onboard 800MHz processor and
256MB of DDR2 cache memory, the con-troller was able to output an average read
speed of 211.7MB/s in a simple HD Tach
benchmark of a four-drive, striped array.
The motherboard-based RAID topped out
at 118.9MB/s.
RAID controllers also offer more options
and safety features than a motherboard-
based chipset, and the motherboard RAID
itself is limited to the number of free SATA
ports you have. In contrast, our controller
supports up to 16 SATA drives.WHY USE A CONTROLLER?
5 MAXIMUMPC NOVEMBER 2007
RAID 5
Parity makes a world of difference and
barely hurts speedsLike RAID 1+0, a RAID 5 confi guration is
a hybrid combination of data safekeeping
and speed. But unlike the former, RAID 5
doesn’t rely on mirroring to preserve your
information. It instead uses an alterna-
tive method of data redundancy found in
RAID setups—parity.
To get into the fi ne nuances of how
parity works would require Excel charts,
lots of binary code, and acronyms—lots
of acronyms. So we’ll generalize. The
mathematics of parity dictates that if
you have four drives in an array, the
RAID will split each piece of data into
three stripes. Each stripe will go to a
single hard drive, as it would in a RAID
0 confi guration.The controller then creates a parity
stripe based on the three stripes of data.
A parity stripe is a logical calculation
that allows the controller to re-create any
individual stripe that becomes corrupt
(or in the case of a drive failure, nonex-
istent). Similar to mirroring, the lost data
is made available to the host machine
instantaneously. But the loss of a single
drive puts the entire array at risk. Should
an additional drive fail—making that two
of the four drives dead—all the data on
the array is lost. A parity stripe works
wonders, just not miracles.HANDS ON
RAID 5 gives you the best combination
of speed, size, and data savings. Our
RAID 5 and RAID 1+0 arrays scored
similar speeds, with the RAID 5 squeez-
ing 15 additional MB/s in our HD Tach
average read test.
The bonus comes in the fact thatour RAID 5 array gave us an additional
drive’s worth of space to play around
with—450 total gigabytes as opposed to
the RAID 1+0’s 300GB of total capacity.
Admittedly, a RAID 1+0 array gives
you better data redundancy on paper,
but the additional mirroring seems like
overkill. In essence, you’d be performing
the same maintenance tasks you’d be
performing in a RAID 5 array. If a drive
goes out in a RAID 1+0, it would be in
your best interest to stop what you’re
doing and immediately replace the dead
drive; the same goes for RAID 5. While
the next drive that goes out in your
RAID 1+0 array might not be the one to
destroy a mirrored pair and consequently
your data, do you really want to roll
the dice? We wouldn’t, and we’d much
rather have the performance and size
benefi ts a RAID 5 array brings.Best scores are bolded.Burst (MB/s) Average Read (MB/s) Average Write (MB/s) Score XP Loading (MB/s) App. Loading (MB/s) Virus Scanning (MB/s) File Writing (MB/s)
RAID 5 457.7 185.3 136.46 1,0510.0 20.85 7.71 126.48 256.36
SINGLE DRIVE 452.1 78.0 102.7 6,329.0 10.42 4.93 77.88 160.51HD TACH PCMARKO5HD TACH PCMARKO5Burst (MB/s) Average Read (MB/s) CPU Use (MB/s) Score XP Loading (MB/s) App. Loading (MB/s) Virus Scanning (MB/s) File Writing (MB/s)
MOTHERBOARD 234.5 118.9 2.0 10,525.0 25.54 12.61 82.53 129.05
CONTROLLER 473.3 211.7 2.0 12,162.0 23.76 9.08 132.57 282.73DONE RIGHTRAID
Best scores are bolded. Arrays were tested using a four-drive RAID 0 confi guration.