With the ever increasing usage of disk based backup solutions, one of the questions I get asked most often is around the future of tape. There is no doubt that disk offers many benefits over tape, not least restore performance and reliability, combined with some great technical advances like deduplication. That said, does tape still have a place in modern data protection?
Rarely a week passes when I don’t talk to a customer who wants to reduce their reliance on tape. The main challenges customers experience with tape are performance, especially when backing up lots of small files, restore speed, and also reliability issues caused by media volatility and drive failures. Add to that the cost of taking tapes off-site and cycling them back on site each day and it is little wonder many want to try and reduce their reliance on the technology.
Disk as a backup technology has been around for many years but, in recent years, has become almost a defacto standard for customers looking for new backup solutions. Disk doesn’t suffer from many of the same reliability issues as tape and the decrease in the cost of network links combined with deduplication and WAN optimisation has meant that replication is now no longer only for the largest customers. Furthermore, disk can be considerably faster than tape for restores, though – interestingly - tape can often outperform all but the fastest disk for backups when backing up certain optimum datasets such as large databases.
Where disk falls down is simply the cost if a customer needs to keep data for extended periods of time – the current street price of an LTO-5 tape is in the region of £35 for 1.5TB of storage capacity which equates to £23.33 per TB (prices may vary). Compare that to disk, where you will likely pay more than £50 for a basic 1TB desktop disk, and you can see the appeal of tape. There are, of course, other costs to both solutions, including drives, enclosures, power, cooling and so on but media alone for media tape offers a significant cost advantage.
Recent analyst studies have shown disk to be anywhere from two to fifteen times more expensive to implement than a tape based solution for long term archive storage and the cost to run and, according to the same study, the cost to run and cool a datacentre could be anything up to 200x more for a disk only solution (http://www.clipper.com/research/TCG2010054.pdf). Added to that, we are about to see the launch of LTO-6 offering 2.5TB native on a single tape with a roadmap planned to LTO-8 which will offer 12.8TB native on one tape and that delta could continue to get bigger.
So am I saying you shouldn’t use disk? Of course not! Disk is a great medium for backup and restores, especially for short term restore requirements which, let’s face it, is where most restores come from – “can you restore my spreadsheet from last night?” or “can you find my proposal from last week?” are common requests that most backup admins hear on a daily basis.
If you only have a requirement to keep data for a short time then disk only will be a great option for you. If you need to keep data for longer, then think about using disk combined with flexible deduplication for your short term backup requirements and then move the data off to tape for long term retention and get the best of both worlds.