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Several new solutions seem demonstrate that backup destination is moving from tape to disk. It isn’t really a new trend of last year (for example see this paper from Lisa 2006, or Microsoft that has removed the tape support in his OS included backup solution starting from Windows Vista), but now more products are pointing to the disk solution.
The Linear Tape Open (LTO) consortium (whose member include Hewlett-Packard, IBM, and Quantum) has officially released specifications for the LTO Generation 5 with around 1,5 TB of native capacity and a throughput of 140MBps (uncompressed)… and is working for the future standards. But also disks are growing, especially in size.
There are different reasons where a B2D could be better than a B2T solution:
- Backup data are growing, due to the big data but also the virtual environment (where usually also an image backup is taken).
- Tape capacity is limited (1,5 TB on LTO5) compared to disk capacity (2-3 TB on SATA disk).
- Tape library are not too much scalable for big backup data or for more parallel jobs.
- Tape drive could be fast (140MBps uncompressed in a LTO5) compared to the average high-capacity SATA disk (around 35MBps), but disks can be “striped” together and also that is a lot of time overhead for a tape look-up and allocation.
- Deduplications can be more effective than a simple compression… but is not really simple apply to a B2T solution.
- Some backup programs (especially most of the specific programs only for virtual environment, like Veeam Backup, Quest vRanger or PHD Virtual Backup) does not handle directly a B2T.
- A B2T solution may required a physical server for the backup program (or the media server), especially for SAS connection (most software vendor does not support a SAS passthrough, also if it may work).
- A restore from a disk (better if it is a RAID5 or RAID10 set) is really faster compared to tape.
But maybe the right approach still remain a B2D2T, because tapes have still some advantages:
- They are design to a off-line archiving… not so easy and simple with disks.
- Tape life could be longer?! Maybe not when are used, but when are been archived
- Tape cost per GB could be lower (but deduplication and disk evolution can reduce disk cost).
Some interesting reading about this:
- Tape Is Dead! Long Live Tape! (from Technet about DPM approach)
- EMC World Boston: The Death of Tape and What’s More Important than Technology
- Tape Backup vs. Disk Backup
Also note that some storage vendors, or some sales representative may tell that storage snapshots can be used a backup policy… this is not really (or totally) true, because at least they can a first protection level, but backup must reside on an different storage, not on the same.