| Much has been written about solid state disks (SSDs) | | | | magnetically coated disks, known as platters, that are |
| becoming the next big thing1 in the IT industry(1). But as | | | | used to store data. This rotating motion of the |
| to whether or not we have enough knowledge of how | | | | mechanical arms results in much wear and tear after |
| it will revolutionize the industry is a different question. | | | | long periods of use. The operational lifespan of a |
| How much do we really know about SSDs? If we are | | | | computer HDD is over three years.(4) |
| to ask people on the streets, it wouldn't come as a | | | | |
| surprise that they dont know much of what an SSD is. | | | | A Flash-based SSD is different. Although the most |
| Even if they do know, most probably it would be | | | | common Flash chips have around 300,000 write |
| limited to a USB pen drive, a CompactFlash or a | | | | cycles, the best Flash chips are rated at 1,000,000 |
| Secure Digital card, which are more on the consumer | | | | write cycles per block. On top of that, Flash SSD |
| side of the storage industry. | | | | manufacturers employ different ways to increase the |
| | | | longevity of the drives. In some cases, they use a |
| Technically speaking, they are not wrong. Most web | | | | "balancing" algorithm to monitor the number of times |
| definitions describe an SSD as a high-performance | | | | each disk block has been written, which greatly |
| plug-and-play storage device that contains no moving | | | | extends the operational lifespan of the drive. |
| parts. Therefore, given that most of the | | | | Furthermore, these manufacturers also designed |
| aforementioned mobile disk storage devices contain no | | | | special "wear-leveling" algorithms where once a certain |
| movable parts, they can certainly be categorized as | | | | percentage threshold for a given block is reached, the |
| SSDs. | | | | SSD will swap the data in that block with the data in |
| | | | another block that has exhibited a "read-only-like" |
| But then again, there's more to SSDs than being a | | | | characteristic in the background. This reduces |
| non-volatile device. The purpose of this article is to give | | | | performance lag and avoids further wearing off of the |
| readers a clearer picture of what an SSD is, its usage | | | | blocks and thrashing of the disk. Even with usage |
| as well as its difference when pitted against the | | | | patterns of writing/reading gigabytes per day, a |
| predominant data storage device at present - the hard | | | | Flash-based SSD should last several years, depending |
| disk drive (HDD). More than its non-volatility, this article | | | | on its capacity. Add to that the inclusion of a DRAM |
| will reveal how much potential SSDs have in optimizing | | | | cache in the disk architecture that further enhances its |
| the performance of the computing system. | | | | operational capabilities as well as lifespan. |
| | | | |
| SSD Defined | | | | Speeding Up |
| | | | |
| Here are several ways the SSD is defined: | | | | With the very fast paced lifestyle these days, most |
| | | | businesses are time-bound and cannot afford a |
| "A solid state disk (SSD) is electrically, mechanically | | | | slowing down in their transactions. This makes speed |
| and software compatible with a conventional | | | | of HDDs a crucial point in technological purchases. The |
| (magnetic) hard disk or winchester. The difference is | | | | typical access time for a Flash based SSD is about 35 |
| that the storage medium is not magnetic (like a hard | | | | - 100 s, whereas that of a rotating disk is around 5,000 |
| disk) or optical (like a CD) but solid state semiconductor | | | | - 10,000 s. That makes a Flash-based SSD |
| such as battery backed RAM, EPROM or other | | | | approximately 100 times faster than a rotating disk. |
| electrically erasable RAM-like chip. This provides faster | | | | |
| access time than a disk, because the data can be | | | | This however raises another point - what's the benefit |
| randomly accessed and does not rely on a read/write | | | | of a high-speed SSD when the entire system cannot |
| interface head synchronising with a rotating disk. The | | | | support it? The evolution of CPUs in terms of |
| SSD also provides greater physical resilience to | | | | performance has far surpassed the development of |
| physical vibration, shock and extreme temperature | | | | the data storage system. The HDD is actually limiting |
| fluctuations. The only downside is a higher cost per | | | | the potential of a computer system when they are not |
| megabyte of storage."(2) | | | | able to keep up with the performance of the other |
| | | | components, particularly the CPU. If an HDD is |
| "Abbreviated SSD, a solid state disk is a | | | | replaced by a high-speed SSD, the performance |
| high-performance plug-and-play storage device that | | | | would significantly improve. The resulting system would |
| contains no moving parts. SSD components include | | | | be a high-powered set-up that can go beyond the |
| either DRAM or flash memory boards, a memory bus | | | | demands of high-speed business or military |
| board, a CPU, and a battery card. Because they | | | | environments. |
| contain their own CPUs to manage data storage, they | | | | |
| are a lot faster (18MBps for SCSI-II and 44 MBps for | | | | Size Matters |
| UltraWide SCSI interfaces) than conventional rotating | | | | |
| hard disks ; therefore, they produce highest possible I | | | | To be a true plug-in replacement for HDDs, |
| O rates. SSDs are most effective for server | | | | Flash-based SSDs are manufactured in standard 2.5" |
| applications and server systems, where I/O response | | | | and 3.5" form factors. 2.5" SSDs are normally used in |
| time is crucial. Data stored on SSDs should include | | | | laptops or notebooks while the 3.5" form factors are |
| anything that creates bottlenecks, such as databases, | | | | used in desktops, or in JBOD or other SAN/NAS/DAS |
| swap files, library and index files, and authorization and | | | | configurations. They can often be used to replace |
| login information."(3) | | | | traditional disks in storage arrays or in a server's |
| | | | internal disk bays. Flash-based SSDs certainly fit the |
| For the rest of the article, we will compare the HDDs | | | | storage needs of most embedded systems that |
| and Flash-based SSDs. The latter are the most | | | | require much smaller form factors. |
| popular type of SSDs employed by the military, | | | | |
| aerospace, industrial and embedded systems | | | | Reliability |
| industries. | | | | |
| | | | In terms of reliability, conventional HDDs pale when |
| Mortality Rate | | | | compared to SSDs. The absence of mechanical arms |
| | | | and spinning platters is the reason behind its reliability. In |
| Hard disk failure is a common occurrence in this age | | | | demanding environments, SSDs provide the type of |
| of desktops and notebooks. A lot of horror stories | | | | ruggedness required for mobile applications. Unlike the |
| have been told, passed around and even published | | | | HDD, SSD's can withstand extreme shock and |
| about how valuable data was lost and the agony of | | | | vibration with data integrity and without any danger of |
| trying to retrieve or at least save a portion of the | | | | data loss. This feature is very important in industrial |
| crashed hard drive. It is during this time that people | | | | applications where exposure to highly combustible |
| wonder, why do hard disks fail? | | | | materials and electromagnetic radiation are typical. |
| | | | Their ability to deliver unnerving performance in |
| The reason is simple - wear and tear. Just like any | | | | extreme conditions also makes SSD play a vital role in |
| good old machine with mechanical components, HDDs | | | | military operations, be it in defense, aerospace or |
| tend to deteriorate over time. HDDs consist of rotating, | | | | aviation applications. |