GROUND zero in this debate is cost. Storage costs a lot – upwards of 40 per cent of the total
cost of system ownership when it comes to video surveillance solutions. And
current numbers indicate that SSD costs three times as much as HDD. The upshot
of this is that it would be quite possible to install an SSD system that cost
as much your HDD-supported entire solution. Yikes.
Of course, SSDs
have good points. Because they don’t have the actuator arm to read the platter
that’s at the heart of an HDD, they read and write to disk faster. This is a
big advantage – especially if you were installing big megapixel cameras and
money was no object.
If your
surveillance application demands a lot of read and storage and you only have a
small storage volume demand there’s no doubt whatever that going SSD will give
you a very noticeable performance boost – especially if you are storing at HD
resolution (720p) or higher.
According to IT
industry commentators, consumer-grade SSDs cost around $3 per gigabyte, while
traditional hard drives cost about 20 to 30 cents per 2.5-inch gigabyte or
10-20 cents for 3.5-inch desktop and server drives. That’s a really big
difference.
But prices for
SSD are falling you say. Well they are but according to IT research outfit Coughlin
Associates’ founder Tom Coughlin, per-gigabyte prices for HDDs and SSDs are
dropping at the same pace – about 50 per cent each year and that means the
comparative expense will remain. Meanwhile, Gregory
Wong, a solid-state drive analyst with market research firm Forward Insights
agreed.
“I think the
issue with SSD adoption is that prices have not been favorable,” he said.
“And there’s still going to be a gap between HDD and SSD prices, even five
years from now.”
A recent
ComputerWorld review undertaken by Lucas Mearian pitted a couple of 2.5-inch
laptop drives – a Seagate Momentus 7200.4 500GB HDD against an OCZ Vertex
Series SATA II SSD.
Mearian tested parameters
like the impact of each drive on battery life, the read and write speeds, cold
boot-ups and restarts, and CPU utilization – all meat and potatoes stuff for
video surveillance people.
“As you’d expect,
the two drives I tested have vastly different prices,” says Mearian. “The
Seagate Momentus HDD (model – ST9500420AS) will run between $127 (all prices in
US dollars, people) and $140, while the OCZ 120GB Vertex SSD goes for between
$376 and $400. Both drives use a SATA 3GB/sec interface and both use cache to
increase write performance. The OCZ has 64MB of cache, the Seagate, 16MB of
cache.
“SSDs are
naturally more rugged than HDDs because they have no moving parts. OCZ claims
its Vertex drive can sustain up to 1,500 Gs of shock before sustaining damage
or a drop in performance. Seagate claims its Momentus drive can withstand up to
350 Gs while operating and 800 Gs when turned off.”
Meanwhile, the
Vertex is OCZ’s second iteration of an SSD, and it uses 64MB of cache to
artificially enhance the write performance and a more advanced Indillinx
controller than its slower predecessor, the OCZ Apex Series SSD, which uses a controller
from JMicron and has no cache memory.
The Vertex
drive’s packaging lists a maximum read rate of 250MB/sec and a sustained write
rate of 100MB/sec. It also claims a 1.5 million-hour mean time between failure
(MTBF) rate, if MTBF can actually be applied accurately to an SSD. Most experts
don’t believe it can.
According to
Mearian, most SSD vendors publish sequential read/write rates, which are much
faster than random I/O but he explains most operations on a desktop or laptop
are random. For example, file systems and e-mail applications mostly use random
operations, while system boot up or copying a large file from a USB drive
involves sequential operations.
How this applies
in a video surveillance application depends on your set-up. If you’re using
record on motion, then read/write is less of an issue – but constant recording
is another matter.
“The Seagate
Momentus 7200.4 marketing material offers no read/write rates, nor does Seagate
offer any information other than a seek time on its Web site: 11 milliseconds
for reads and 13 milliseconds for writes,” explained Mearian.
“Seagate doesn’t
use MTBF, preferring its own annualized failure rate (AFR) metric as a method
to gauge drive reliability, which is .5%.
The SSD easily
beats the HDD in weight. Seagate’s Momentus weighs 3.85 ounces; OCZ’s drive
weighs 2.7 ounces.”
Test times
Mearian says the
Vertex SSD handily beat the Seagate HDD for cold boots.
“It was 20
seconds to start up Windows XP for the OCZ and 40 seconds for the Seagate. The
SSD also beat the HDD for restarts: 26 seconds versus 37 seconds. While it may
seem odd that the Seagate drive performed better on a restart than on a cold
boot, keep in mind that the drive is still spinning and plenty of OS data is
still residing in memory,” he says.
“The drive also
has native command queuing (NCQ), which allows its controller to prefetch data
in order to access it more quickly on reboots. It works in the same way a
grocery list helps you find products as you enter the store. OCZ’s Vertex drive
with Indillinx controller also has NCQ.
“When it came to
I/O speed, there was no match. I used ATTO Technology’s ATTO Disk Benchmark
v2.3.4 and Simpli Software’s HD Tach v3.0.4 benchmarking utilities to perform
my read/write performance tests,” Mearian explains. “The ATTO benchmark
software showed the OCZ had a read time of 244MB/sec and a write time of
172MB/sec. The Seagate HDD had an average read rate of 98MB/sec and a write
time of 87MB/sec.”
But Mearian says Using
HDTach, the read/write results were quite different. OCZ’s drive showed a
196MB/sec read rate, the Seagate, 84.6MB/sec. The HDTach software also measures
CPU utilization and random access times. OCZ’s drive had a random access time
of .2 milliseconds; Seagate’s 16.9 milliseconds.
“While Seagate’s
slower random access time wasn’t surprising, I was surprised that it actually
beat the OCZ drive on CPU utilization: the OCZ SSD used 8 per cent; the Seagate
HDD used 5 per cent.
“For my next test
I transferred a 1GB folder filled with photos and video files to the drives
from a USB drive. Both the SSD and the HDD accomplished the file transfer in
about 50 seconds (the Seagate was 2 seconds slower),” Mearian says.
“For the battery
test, I used MobileMark 2007 benchmarking software from Business Applications
Performance Corp. (BAPCo). The software simulates more than a dozen programs
that people use in everyday life, so it’s considered a very accurate
measurement of power consumption, and the results from this test were the
biggest surprise of all. The battery lasted 132 minutes when powering the
Seagate drive and 137 when powering the OCZ – only a five-minute power
difference.”
But Mearian says
while the SSD outperformed the HDD in most benchmarking tests, as well as
handily beating out the competition for boot-ups, whether or not you should
choose an SSD over a HDD will depend on your needs.
“HDDs, especially
those with 7,200-rpm spindle speeds or higher, offer respectable read/write
rates and vastly higher capacity levels to SSDs,” he says.
“For most users,
this a good time to consider buying a higher-end HDD that should deliver more than
enough performance and plenty of room to grow while you wait for SSD prices to
drop further,” Mearian says. “But that could be a long wait.”
