With the performance boost as well as power savings that SSDs have to offer, the comprehensive move from mechanical drives to Solid State Disks is an inevitability, While the PC user faced an almost immediate phasing out of 3.5 inch floppy disk drives (let’s forget the brief Zip drive era) for GB USB sticks, surely the drive for tiered storage based upon different grades of SSDs should be just as rapid? But this hasn’t been the case with one left wondering as to why?
The first obvious answer is the price. Not many companies are prepared to fork out the extra 30 times price hike for SSDs to the already expensive magnetic disk drives they purchase.
The other and more controversial answer are the storage vendors themselves. Not yet amongst the big daddy of corporate companies, the production of SSDs are still limited to vendors not necessarily linked or partnered with any of the major storage vendors. Hence they can only market their products to consumers via the Storage vendors that already have their mechanical disk platforms in place in just about every datacenter in the world. Hence the emergence and availability of the readily compatible Flash drives ahead of the more complex DRAM SSDs.
Despite the obvious advantages of DRAM SSDs over their Flash counterpart , the marketing has been pushing for the ‘future of flash’ and their compatibility with the already existing storage systems. While it doesn’t take rocket science to realize that the storage vendors wanted to ensure that their current hardware didn’t prematurely pass their shelf date with the rapid development of SSDs, the marketing ploy stating that flash drives would provide superior performance can now be seen to be nothing more than hyperbole aimed at generating Google-keen I.T. Directors to part with their budgets.
The fad was clear: push flash drives as the new ‘super’ tier one, thus allowing customers to embrace the inevitability of SSD while still maintaining the sales and maintenance of current storage systems which could have flash drives installed in their back end. A good deal for the storage vendor but not so great for the customer or the developers and small companies who were producing SSDs of far superior quality and performance to the currently compatible flash drives.
So what exactly is the problem with Flash drives in comparison to DRAM SSDs?
Firstly their life time due to their limitation of erase/write cycles. Unlike DRAM, Flash is limited in the number of times it can be erased and rewritten which poses the problem of a write failure in the middle of a database transaction. All the redundant hardware and setup of your infrastructure becomes compromised with the risk writes which have already been committed being at risk due to a potential write failure. Coupled with the fact that Flash drives currently have no Self-Monitoring, Analysis and Reporting Technology, something which is found in magnetic disks and automatically monitors a disk drive’s health and reports potential problems. Hence proactive actions can be taken with magnetic disks to prevent impending disk failures but not so with Flash.
Furthermore the marketed performance improvements of Flash over their magnetic disk counterparts also need to be looked at with a shrewd eye. While DRAMs would sit in the front end cache, Flash disks reside on the back end of a storage system. That means behind a RAID controller, which is behind controller cache, which is behind storage port controllers, which are behind a SAN, which is behind a server! Hence purchasing Flash disks on the backend may not only be uneconomical but also illogical when placed in a situation where most I/Os are dealt with by front end hits to the cache. In addition when some applications stage the majority of I/O requests to server memory then the marketed advantages of Flash become very dubious certainly not 30 times greater than their magnetic cousins.
Undoubtedly the underlying point remains that It’s not a question of if, but when the mechanical drive will be made extinct by SSDs.
Developments such as Pliant’s claim that their 3.5-inch enterprise solid-state drive is able to run at speeds of almost 500 megabytes per second and can write the data at a speed of 320 megabytes per second, SUN Microsystem’s new 2TB SSD F5100 array and 2001’s announcement that their 2.5-inch SATA SSD will have built-in ECC (Error Correction Code) functionality all make it clear that while the future might not necessarily remain flash it certainly will be solid.