3 ms·
I don't know about the drives themselves, but a company I worked for once used large, robotic arrays with 16 drives each. Typically they ran 15 drives writing (
by hotpotamus 3y ago
I don't know about the drives themselves, but a company I worked for once used large, robotic arrays with 16 drives each. Typically they ran 15 drives writing (backups) and left one idle for reads (restores) as needed. The tapes were on the order of a kilometer long, so considering the time for a robot to pick the tape and seek to the proper spot, latency is pretty high in the best of circumstances (no one else is using the one reader drive when you request it).
- londons_explore 3y agoBut the drives that are doing writing... Either they are writing onto an entirely new tape, or they're writing over an existing tape. If it's an existing tape, you need to make sure that everything on the tape is not needed anymore. Yet commonly 75% of the data on the tape isn't needed anymore (retention period expired), but some might still be needed. Unless you have a hard drive somewhere with another copy of the data, you need to read every tape before rewriting it. I suspect your use case is strictly for backups, whereas my use case is more archival (where all copies of the data are on tape, and there are no copies on hard drives).
- lwkl 3y agoThey can also append data to an existing tape. These tape libraries can also defragment tapes. For this all the data that needs to preserved is read from the tape and written to another tape. Even for backups you have a consolidation/defragmentation task running every so often that frees up space on the tapes and only keeps the backups you specified in your retention policy.