On Tue, 8 Dec 2009 at 5:02pm, ckotil wrote
With my LTO3 drive, and 2x500GB sata 7200rpm drives in raid1. When I write from disk to tape I can hit 55MB/sec max. However my dumps are often much larger than the holding disk. I am forced to stream data to the tape drive which slows the write. Typical write to tape speed for a dump averages 20MB/sec. When writing to tape I can dump 100GB in roughly 1 hr and 45 min. Im sure with a proper config I could make my dumps more efficient. In the amanda.conf, tape type is accurate. I think the flush-threshold settings could use some tweaking to better utilize the limited holding disk.
LTO3's native speed is 80MB/s. AFAIK, it can only throttle down to half that. Any slower than that and you are shoe-shining your drive, which is bad for your tapes and drive. You *really* want to either a) increase your holding space to accomodate your biggest DLE or b) split your over-large DLEs into multiple holding-disk-sized DLEs.
-- Joshua Baker-LePain QB3 Shared Cluster Sysadmin UCSF
