LTO Tape

Attachment 1558

I thought I'd make a topic about my LTO 4 tape drive since we all love storage :).

I'm doing a lot more video than I used to and keep running out of space. So I decided to get an old tape drive. LTO4 is quite an old generation of the LTO tapes (it was introduced in the late 2000s), and holds 800GB per cassette (the latest versions store 10s of terabytes). This is a very useful amount for the kind of data I have.

LTO 4 machines are quite cheap now on the second hand market (I think I paid about ?60 for mine). Old stock and second hand tapes are quite cheap. I've just got some second hand ones from a recycler for about ?2.50/each - half of them had only been used once or twice and the others had been used more but have plenty of life left in them.

How do I know that? LTO cassettes have an RFID chip inside them which contains the manufacturer, serial number, date of manufacture, as well as how many times it has been loaded into a machine, how much data has been written to it, and how much has been read from it. A good way to figure out at a glance what sort of condition a tape is in.

Tape is actually very easy to use in Linux. The SAS interface cards and the tape drives are "plug and play" as the drivers and control software are built in to Linux. The 'mt' command is used to shuttle around the tape. The 'tar' command is used to archive files and record them on to the tape. The commands can be a bit of a mouthful when you're starting out but they're quite easy once you've got the hang of it.

Tar can be used to archive an entire large HDD and span it across multiple tapes - it will simply prompt you to insert the next tape when one is full - ideal for backups. But it can also be good for storage - so if you want to archive some large files from a camcorder, you can make multiple tar files on the tape - one file for each project, then just write on a sticky label which file is which :).

The only problem is speed. The tape drives themselves are quite fast. They can slow the mechanism down to accommodate a lower data rate if needed, but there is only so slow it can go. If you are loading large files (video, disk images, photographs etc) off an HDD, the computer can read these very quick, and the tape drive can record them very quickly. But if you have thousands of tiny files (e.g. text files), the HDD cannot load these up quickly enough, and the tape drive will have to stop and start. This necessitates the use of a memory buffer which makes the commands a bit more complex, but again, once you've figured it out, it works quite nicely.

I've had this setup for about a year now and it works very nicely, and is very cost effective. The second hand equipment I have combined with an assortment of tapes works out at about ?10/TB.

But when you think about it, it really shows how amazing hard drives are. In the photograph, there is about 15TB of storage space. That's about 10 miles of half inch tape! An HDD would store that on just a few small platters :).