bwDataArchive relies on mangnetic tape technology for the long term storage of data, as it is less expensive than the use of HDDs or SSDs. As a result, there are several unique characteristics and restrictions to consider when using this storage service:

• Files are first written to a hard disk/SSD cache and from there transfered to magnetic tape. For each file, two copies are written and stored at different locations. Additionally, the checksum of the file is calculated. Once the file was successfully transferred to tape it is marked for deletion/overwrite in the disk cache.
• To retrieve a file from storage, it may need to be copied from tape to the disk cache before it can be delivered to the user. As files are written sequentially on tape, this can take several minutes per file.

We therefore impose the following restrictions for the use of bwDataArchive:

• To limit wait times for a single file we impose a maximum file size of 600 GB. Files larger than this will be rejected by our system and will result in transfer error messages.
• The service has no possbility to check if a file transfer was correct and complete. It is the responsibility of the user to check if a transfer was completely successful. To this end, the user may retrieve the checksum of a single file here.
• If possible the user should refrain from writing files with sizes smaller than 100 MB. Accessing many small files is more laborious and time-consuming than accessing one large file, which may lead to larger wait times before a file can be accessed. Small files should be gathered in archive-files (such as .zip, .tar, .rar) prior to upload.
• Files should not be changed once they have been uploaded successfully. As files are written sequentially to magnetic tape, later changes or additions to the file may have to be read from a different place on the tape or even an entirely different tape cartridge. Should you wish to write a new version of a file, please erase the old copy of the file or overwrite/replace the entire file. Excluded from this is the case that you wish to resume an interrupted transfer shortly after the interruption occured.

Offered access protocols:

bwDataArchive currently only offers access via SFTP.