Dear developers, (Please CC me as I am not subscribed (yet))
Writing (backing up) to multiple optical drives at the same time results in a performance loss of about 7-10 times compared to writing to a single drive. After digging around it seems the problem arose about 5 years ago after the Big Kernel Lock removal and the introduction of the new "sr_mutex" private mutex in drivers/scsi/sr.c, which locks on a per driver basis instead of a per device basis. Various reports by users are listed on this issue on various mailing lists, so I think there is interest for a solution in the linux community. So far, it looks like this has not attracted the attention of, or not been identified as a priority by, any of the kernel developers. However, I think a Linux based DIY server with multiple optical drives for the purpose of backing up files in multiple offline copies is a very useful application and it would be unfortunate if the current behavior keeps such an application unfeasible. Would someone be willing to look into this and/or comment on the issue? Sincerely, Johan de Jong
