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Regular splashes back then for instance, were articles proclaiming the 'Death of Tape Backup'. Tape-based backup technologies were apparently under serious and terminal threat from the ever increasing in size Hard Disc Drives (HDD) with an ever decreasing price tag. As a result, it would surely only be a matter of time before tape disappeared altogether making way for Virtual Tape Libraries (VTL) backed by HDDs. Soon after, Disk to Disk backup (D2D) was a hot topic and almost every storage vendor had a D2D backup appliance offering of some sort, in fear of the inevitable death of tape backups.

Sure, all this fanfare did increase the utilisation of disk based backup solutions and started somewhat of a disk based backup trend in the market, steadily usurping in to tape's territory. However, as things turned out, complete death of the tape backup has proved not to be the case yet.

While there was a clear use and often an important place in the enterprise data centre for the use of disk based backups, the poor old tapes still carry through as the final destination of a typical backup cycle for most organisations, where long term retention at a minimum price point is key. One can argue that this is because old habits die hard, but it would be more logical to deduce that's because they both have their rightful place in today's data centre - given their individual characteristics for different use cases.

FLASH FORWARD
Similar to that debate, HDD is now finding itself under threat from solid state and flash storage technologies at present. Flash storage is far from fledgling and with its latest incarnation of Solid State Device (SSD), has been around in varying flavours since the 1980s.

While flash has enjoyed huge popularity in smaller, consumer devices (tablets, smartphones, cameras etc.), SSD is gaining serious traction in larger high-end applications - up to and including enterprise-class storage arrays. Almost all legacy storage array vendors have an all flash (SSD) SAN offering available now, while a raft of Silicon Valley based startups have also sprung up specialising in just offering All Flash Array (AFA) storage solutions to meet every enterprise storage requirement.

The undoubted technical advantages of flash are obvious; it offers nanosecond seek times (aka. ultra-low latency) against the milliseconds of mechanical HDDs. It is also much quieter than HDD technology, more compact, uses around 50% less power and - with no moving parts and a much greater resistance to high-G bumps and drops - is extremely reliable and robust too. But most importantly, flash storage is capable of performing an obscenely high number of Input Output (IO) operations. Often a single SSD can outperform the collective throughput of a substantially high number of HDDs together.

THE RAW TRUTH
Despite the advantages of flash, the consensus agreement is that flash capacity costs more per raw unit of storage (GB) compared to HDD. This is true as flash uses more expensive NAND technology in comparison to cheaper mechanical disks used by HDD. As a result, many enterprise SAN vendors have had to come up with innovative techniques to maximise the use of flash capacity through the use of inline de-duplication and in-line compression of data, prior to being written to flash - effectively optimising the useable capacity. At the same time, it should also be noted that the cost of flash in general has been gradually coming down and capacity has been going up.

The evolution of the SSD storage technologies from expensive SLC (Single Level Cell) to MLC (Multi Level Cell) and the invention of new TLC (Triple Level Cell) technologies are all signs of flash storage continuing to become cheaper, while also increasing the capacity in time to come. This is likely to move in the same direction in the future and will therefore be the preferred choice for many workloads. It's worth noting however, that at the same time, HDDs are also growing in capacity and further reducing in cost, maintaining their cost per GB advantage over flash somewhat. It is reasonable to assume that this trend will continue in to the future and as such HDDs are very much likely to continue to maintain this price and capacity advantage over SSD for the reasonable future.

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