Is it time to move to SSDs?

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.

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