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Five types of tape for backup or archive
There are plenty of tape formats to choose from when you are looking for a backup or archival medium. Here are five of the most common formats to consider.
Tape is, apparently, dead.
But that doesn’t users from buying tape. Analyst firm The Santa Clara Consulting Group’s most recent Back-Up Tape Tracker, the 2011 Global Review (PDF) reports that “Back-up tape drive and media sales represented a $US1.56 billion market in 2010.” Both markets grew in 2010.
No wonder the likes of Oracle, HP, IBM, Quantum, Tandberg Storage and others are duking it out for market share in the space.
So why is tape still with us? The reasons are simple: tape is reliable, long-lived and well-understood storage medium. It may be slow – and therefore not the best choice if you need a short recovery time objective – but tape also, for a while at least, offers greater capacity in a single unit than disks. That density advantage is under threat as disks increase their areal density, but tape can counter that it can store data without needing to consume any electricity.
Those useful qualities mean tape is still a favoured archival medium, so much so that there are several competing standards for you to choose from.
The main formats are:
- LTO
- DLT-S
- DAT
- AIT
- QIC
Let’s have a look at each
LTO
LTO is now the world’s dominant tape format: Santa Clara Consulting Group (SCCG) says it accounted for 91.18% of drive and 83.58% of tape cartridge revenues in 2010.
It’s not hard to understand why: the standard is developed by and jointly overseen by HP, IBM and Quantum. Tandberg Data, Fujifilm, Imation, Maxell, Sony and TDK make either drives or media using the standard.
The LTO roadmap is long: LTO-5 is currently on sale but the LTO partners have already planned LTO-8. When the format reaches the latter milestone it is projected to offer 32 TB capacity and up to 1,180 MB/s data transfers (both assuming a 2.5:1 compression).
LTO is also future proof inasmuch as the partners behind the standard have committed to making it backwards compatible: a new LTO drive can always read cartridges from at least two previous generations.
DLT-S
SCCG rates DLT-S as the second largest source of tape sales, by revenue. A premium version of the DLT standard, DLT-S has its roots in minicomputer tapes devised by Digital Equipment Corporation.
DLT-S tapes offer up to 800GB per unit and transfer data at a relatively anaemic 60 MB/s. It’s hard to imagine anyone buying DLT-S for a new backup or archiving job these days, but the standard’s long history – it’s been around since 1984 – mean there’s a sizable installed base hungry for media and new drives. Quantum is the main source of hardware.
A less resilient cousin, DLT-V, clocked drive sales of $2.64 and cartridges sales of $14.86 million in 2010. Those low numbers tell you all you need to know about the significance of the format.
DAT
A throwback to 1980s attempts at replacing the compact audio cassette, Digital Audio Tape (DAT) was pressed into service as a data storage medium quite early in its life. Sony developed and owned the standard, and SCCG found $US52.28 million of drive sales and $US39.11 million of media sales in 2010.
Most would have been either DAT-160 or DAT-320 devices or media, with the former offering 80GB per tape and the latter 160GB.
The DAT Manufacturers Group promises a new generation of DAT around two years after 2009 and in the DAT roadmap says it will have around 300GB of capacity.
That low capacity, plus a planned data transfer rate of just 16 MB/s are the reason DAT has never really escaped a small business niche.
AIT
Sony’s Advanced Intelligent Tape format is interesting inasmuch as its cartridges include a small amount of flash memory, which means directories describing each tape’s contents can be stored on the tape itself. This helps speed access to data and is useful in some archiving applications.
The most recent AIT-5 tapes can reach 400GB capacity and transfer data at 24MB/s. Again, the small size and slowish speeds mean this is not mainstream format.
QIC
SCGG sees some life in quarter inch cartridge (QIC) tapes, which sold $US18.99 million worth of product - 36.42% for drives and 63.58% for media – during 2010.
