Solid state drives (SSDs) are the future of current hard
drives. If you were asked to list one component that typically fails in your
computer; you would probably say HDD! This is mainly because of the mechanical
nature of the drive, which involves rotating platters and moving read-write
heads. NAND memory has surfaced to become the alternative storage solutions for
such mechanical drives. The solid state drives on the other hand, uses no
moving mechanical parts but rely on non-volatile NAND flash memory. Since,
there's no actuator arm that moves read-write head to seek data on the hard
drive platter, they are faster in reading and writing data. In every aspect, a
SSD is same as a conventional hard disk drive having same interface and
software model, but what differs in them is the significantly higher speeds,
lesser power consumption and silent operations. Because of such enhanced
performance gain over traditional hard drives, SSDs have not only become the
latest fad amongst technology enthusiasts, but is also positioning itself for
organizational use including servers.
The only thing that negates these performance gains and
other benefits of solid state drives over conventional hard drives is the price
factor. In this article, we compare the advantages and flaws of SSDs against
HDDs, and see if upgrading your system with SSDs by replacing HDDs is
viable.
Why are SSDs faster?
Hard disk drives incorporate rotating magnetic platters that have data laid
out within tracks across the surface of each platter. To read and write data,
the hard drive incorporates a mechanical actuator to move recording heads across
the platters as it spins. Therefore, the time involved in moving the heads (seek
time) and the time taken to bring the desired data under the head leads to
latency, which is the bottleneck in maximum HDD performance. Though, the HDD
manufacturers are increasing the rotational speed of the platters and trying to
shorten the seek time, the latency persists. This isn't the case with SSDs.
On the other hand, SSDs are basically flash memory drives
and have no moving mechanical parts, which means there is no mechanical seek
time or latency to overcome. SSDs comprise of two design technologies, SLC and
MLC based NAND flash technology. SLC format is of single level cell, where each
memory cell holds one bit and MLC (multi level cell) is the method to achieve
higher capacities as each cell in memory can hold two bits of data in duplex
mode. Higher capacity SSDs are mostly having MLC flash memory drive. Thus,
solid state drives, which do not have any disks, don't require any initial
spin-up of platters and read-write heads. Due to this, SSDs can transfer data
out as soon as it is read off from the NAND flash memory. Therefore if there is
an application that has most random data requirements, a SSD will deliver more
performance than a HDD. In a HDD, the drive head will have to move to and fro to
access the randomly located data that will result in greater seek times. The SSD
will have no such issues and thus would perform better due to virtually null
seek time. Also, since no spin-up of platters is there, the solid state drive
consumes lesser power at start up when compared to conventional hard disk
drives.
Advantage of SSDs
Besides performance SSDs have other benefits over regular HDDs as well.
Having no moving parts allows SSDs to manage failure modes differently. In case
of HDDs, a head-crash can result in immediate failure of the drive. Whereas,
SSDs can have multiple cells to degrade and fail over time before the consumer
faces the actual failure. SSDs are more durable than their counterparts as they
can withstand shocks of upto 1500G, no matter it's in operating mode or not.
HDDs can withstand shocks of up to only 400G while the drive is operational.
This durability of SSDs has prompted the military usage of SSDs in battlefield
conditions or in supersonic fighter jets, where due to vibrations a conventional
drive can cease functioning.
Besides being light weight to their equivalent hard-drive
counterparts, SSDs provide a security advantage also. The data is not always
written in sequential tracks in the hard drive, and when a file is deleted its
traces can still be recovered from the tracks. Whereas, in case of SSDs a file
that's deleted leaves no residual data behind to recover.
Since, SSDs lack any moving parts there is actually no
sound emitted from the drive. No moving parts are also the reason that lead to
higher reliability of SSDs and lower power consumption.
Disadvantage of SSDs
Though SSD manufacturers have now started offering higher storage capacity
within same form factor (2.5” drive) as those offered by the HDD manufacturers,
they are yet to bring the cost of solid state drives to be compared at par. Even
an entry level 64GB SSD would be costing more than the price of a regular 2.5”
500GB laptop hard drive. The two drives, one SSD and other HDD, which we used
for performance testing, too has a very huge price gap. Though both the drives
have similar storage capacity of about 500GB, the difference in price per GB
ownership for each drive is astounding. The per GB cost for HDD was Rs 12.8,
while the per GB cost of SSD came out to be Rs 144.5. This huge price difference
prevents SSDs to come into mainstream usage.
Performance Tests
SSDs can improve system performance is a known fact. The biggest bottlenecks in
a computer today in terms of transfer speeds is still the hard disk. Even the
fastest processors have to wait to read and write requested data. And since SSDs
are memory chips after all, they give faster response times and higher
read/write speeds. Thus, SSDs make a huge difference in speeds of applications
where data is to be frequently read and written to the drive. To bring that
forth we decided to perform real-life application tests rather than benchmarks
on two drives, SSD and the conventional HDD, of same form factor and capacity.
The Kingston SSDNow V+ Series 512GB 2.5” SSD was compared to a standard notebook
HDD having 500GB capacity, 7200rpm and 16MB cache.
We tested the drives on the same setup that comprised of
AMD Phenom II X4 3.21 GHz based machine having 4GB RAM. Since, both the drives
were fresh; we performed clean installation of Windows 7 Ultimate on both of
them. To check if there is performance difference in speed of application if run
on SSD as compared to HDD, we decided to run a test that would comprise of a
hard-drive intensive application, and what better than a antivirus scanning
process to do that. To do so, we copied the same dump of test data amounting to
10GB on both the drives, and ran Avast 5 Free Antivirus. For the complete system
scan feature of the antivirus, we enabled the reporting feature as well with all
options selected, so that during scanning while the files would be read, there
would be a simultaneous write operation on the drive going on as well. This
generated a 23MB report text file at the end of each scan task in both the cases
(The complete system scan included the Windows 7 files and the 10 GB test data
dump, amounting a total data tested in both cases to be of about 28GB).
The complete scanning process took 23 minutes and 42
seconds in case of conventional drive; while on Kingston SSDNow 512GB drive the
complete scanning process was finished in 18 minutes and 43 seconds. That is, a
time difference of almost 5 minutes for scanning the complete drive. From this
it can be attributed that SSDs can deliver faster performance for applications
that are hard-drive intensive. We also ran the HD Tune benchmark to evaluate
performance, and Kingston SSD gave astounding average transfer rate of 177.1
MB/sec with an access time of 0.3ms, while the conventional 2.5” 7200rpm HDD
clocked average transfer rate of 85.7 MB/sec with 17.1 ms of access time.
Even the latest operating system, Windows 7 has been tuned
to work efficiently with new generation of SSDs. The Windows Experience Index on
Windows 7 gives a better rating when it is installed on SSD rather than on a HDD.
On Kingston 512GB SSD, the rating for primary hard drive component shot to 6.9
while when Win 7 was installed on the conventional high-end HDD the same
component rating was 5.9.
Conclusion
Thus, SSDs churn out better performance when compared to HDDs, but price is
the major concern. SSDs can reach the capacities of mainstream HDDs, but
replacing them totally is yet a distant dream. In organizations, where there are
applications that require higher IOPS (Input Outputs per second), SSDs can give
better performance to regular hard disks. Such applications would not require
much drive capacity and therefore even a 64GB or better a 128GB SSD can provide
sufficient space for OS, application and its data files and in turn will churn
out higher performance when compared to other enterprise class hard drives.
Because, to achieve such performance gains in enterprise applications, the price
per GB would not be a limiting factor.
Despite SSDs having faster speeds, meaner on power
consumption and highly durable over conventional hard disks, they are not yet
poised to replace HDDs from desktops or notebooks. Neither the faster
performance nor high durability of SSDs can compensate for the price factor, due
to which HDDs will still remain to be widespread in usage because of their
affordability. Though, in enterprises for high IOPS applications and in military
purposes, SSDs are the best option. Unless you are a technology enthusiast, the
benefits of solid state drives are not that significant until the prices of SSDs
come down significantly.