I have the same issue. I have a SDLT/320 tape drive, capable of 56 Gb/h. My holding disk is a two 73x10k Gb SCSI U320 Raid 0 array, and in my reports the total tape time is much smaller than the run time, since my tape writes at ~16 MB/s and the dump speed to the holding disk performs only at (depending on the disk being dumped) 5-7 MB/s. I think the dumpers and the taper compete for I/Os, when they access the holding disk at the same time, the dumper for writing and the dumper for reading.
Cheers, -- Iñaki Sánchez Servicios Informáticos Universidad de Navarra Ed. de Derecho, Campus Universitario 31080 Pamplona (Navarra), España tfno: +34 948 425600 Ext. 2106 http://www.unav.es/SI Guy Dallaire wrote:
There was a recent discussion on the list regarding ultrium LTO3 tape speed/performances. According to my vendor, the LTO2 drive I'm about to buy is capable of 80Gb/Hour, that is approx 50 Mb/Sec if I'm right. I'm currently using an adaptec AHA2940U adapter with my DLT4000 drive. I think it's only capable of 20 Mb / Sec... I have a couple of question: What adapter should I buy to feed the LTO2 drive ? It need to be compatible with centos 4.2 (RHEL 4 clone) Provided I buy the correct adapter along with the tape drive, and my holding disk is dedicated to amanda (it's a single 200 Gb ATA drive) how am I to know (measure) if my tape server is feeding the tape drive appropriately ? Would I be better using an SATA drive instead of an ATA drive ? Wouldn't the dumpers compete for I/O's on the holding disk with the taper process ? Or does the taper process begins writting to tape only when all the dumpers have finished ? Where sould I look to see if my tape drive is fed properly ? Thanks