Job Rate

Hi,

We have BE 2010 R2 that works with a  Dell backup library, I have 4 jobs that for last 3 years works very good, but since 2 days ago my differenatial back-up job has a really low Job rate like 114 MB/min. the same job untill 2 days ago has an 1716 MB/min job rate. so the same job that every night take about 45 min to backup 100 GB data, now take us like 13 hours.

Nothing has been change on the media server side or the job. any idea why the job rate is too low? and how can I solve this issue.

Thanks