Copying data to tape is called Archiving, as its goal is to be an independent copy of data that doesn't rely on other backups to be retrievable. Archiving with Canister is simple:
First, select the disk or folder you want to archive by either dragging in a folder from Finder or by browsing to a Source Folder. Then continue, and mount a tape. Next, confirm the transfer(s).
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. Canister reserves 5% of the free space for indexes, resulting in a more realistic free space calculation:
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.
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.
Like with Hedge, Canister allows you to combine folders and files into a Collection to be used as the source for your transfer. Canister accepts any combination of files and folders that is stored on the same volume.
To create a Collection, either multi-select files and folders in Canister's source browser, or simply drag and drop a selection from Finder into Canister's source view.
Canister will order the files-to-be-archived logically so that they won't end up on your tape in a defragmentated order.
Canister automatically applies Duplicate Detection to all transfers. When a file is identical in name, size, and modification date, it is skipped. When a file has been changed, the already stored file will be renamed by appending its modification date and hidden. That means all previous versions of a file will always be available for retrieval at a later time.
As Canister comes with Duplicate Detection, it will detect what is new or has changed and only copy those files and folders to tape. Keep in mind that due to the linear nature of LTO, this will cause your data to be stored in different sections of the tape and thus will impact retrieval time as the tape head has to make a lot more movements to access a folder's contents across a tape.
Canister can write to multiple drives at once. If the tapes used are of equal generation and thus speed, it will be as fast as writing to a single tape. However, there may be a bit of deviation as tape drives often have slightly different speeds.
Preferably, use a faster-than-tape source for maximum write speeds to tape and speed up verification.
When selecting files to be archived, often files that appear to be consecutively and part of the same folder are not actually stored in consecutive order on disk. When working with LTO files must be lined up and written in consecutive order to prevent shoe-shining upon retrieval. Canister handles this for you, ensuring files that live together in a folder will also live next to each other on your tape.
Many legacy systems use a deny-list of characters, severely complicating many workflows. To solve that without relying on a database and thus introducing vendor lock-in, Canister utilizes percent-encoding for all illegal and unsupported characters. You cannot only use any of the forbidden characters
/ * ? < > " | \ :but also use any internationalization in all file and folder names. Canister will know when it needs to replace them and when not to.
Upon retrieval, Canister automatically converts percent-encoded characters back to Unicode. If you make use of illegal characters heavily and plan to retrieve a Canister-made LTO with a different mechanism or app, it's easy to use a percent-decoding script after doing the retrieval.
By default, each archive is fully verified by reading back the files after being transferred. Verification can be skipped at any time by clicking the
xbutton next to the progress bar.
By default, Canister uses
XXH64BEfor verification. For legacy workflows, it's also possible to use MD5. Or, disable verification altogether in Canister's Preferences:
LTO drives offer built-in hardware compression. Compression is a property of a tape and is set to use compression when formatting the tape. After the property has been set, it cannot be removed without again erasing the tape. As the compression has zero to no overhead, there's no reason to disable it. As the compression happens in-device, there's is no feedback on the process, or on how much data is actually saved.
Although touted as a big feature for LTO, don't expect any wonders from it. LTO compression only works well for text files and not at all for video or photo material, so never expect to be able to save more data to a tape than the bare capacity.
Canister currently does not support hardware-based LTO encryption.