Tape Media
Generations
Every few years, the Ultrium Consortium (consisting of IBM, HP, Quantum, and tape manufacturers Sony and Fuji) releases a new version of LTO. These versions are known as generations. Each generation holds more TB per tape, and sometimes newer drives are also faster.
As any generation older than LTO-5 does not support LTFS, we don't take these into consideration.
Tape Capacities
With all the marketing that surrounds LTO, it's good to set things straight from the get-go; the advertised tape capacity is not a realistic value.
The advertised capacity is a raw byte count, and doesn't account for file system overhead and the space the index partition will require.
9
18 TB
17.5 TB
16.7 TB
8
12 TB
11.7 TB
11.1 TB
7
6 TB
5.73 TB
5.4 TB
6
2.5 TB
2.45 TB
2.3 TB
5
1.5 TB
1.43 TB
1.4 TB
As not having enough free space for the indexes results in unmountable tapes, Canister reserves 5% of the free space for indexes. The result is a more realistic free space calculation, as shown in the last column.
If required, you can decrease this reserved amount of space using this Terminal command:
defaults write nl.syncfactory.Canister.Mac ReservedTapeIndexPercentage n
where n stands for the percentage integer, e.g. 5 for 5%.
Be very careful with this setting: the few extra GBs you'll gain might not be worth the trouble. If you decrease this value and end up putting too much data on a tape without sufficient room to spare for the index, LTFS won't be able to finish writing the index. The result is a tape that will no longer mount. You can consider the data to be lost, as you need to reformat the tape to be able to use it again.
WORM Media
As Write Once Read Many ("WORM") tapes cannot be partitioned, they are incompatible with LTFS. Be sure to use rewritable tapes with Canister.
NanoPureā¢ Support
In the event of a poor result you might consider retiring the tape, or contacting your hardware vendor for a thorough diagnostic check.
Tape Initialization
Up to LTO-9, tapes do not require initialization. When inserting a new LTO-9 tape into a drive for the first time, the LTO drive will spool through the whole tape. This process can take as long as two hours and is indicated on the Single Character Display as a lowercase c. For convenience, some vendors like Symply sell pre-initialized media.
If your drive is of an older generation that LTO-9, you can simply insert a tape and continue with formatting.
Migrating
While the LTO consortium touts a 30-year lifespan for tapes, their hardware definitely won't last that long. That's why it makes sense to migrate your archive to a newer generation once every few years. How often depends on the size and value of your archive.
Here's how many tapes you can migrate to a newer generation:
LTO-5
8
12
LTO-6
4 or 5
7
LTO-7
2
3
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