01-17-2014 02:07 AM
scenario:server HBA port supports 4g and current speed 4gps and My tapedrive current speed 8gbps.i have mapped this drive(8gbps)with server hba(4gbps).
my question here what is the maximum data rate transfering?4gbps or 8gbps?
what is the best practice to utilize the max speed from both ends.
01-17-2014 02:21 AM
hi, the HBA will be running at 4Gb and the tape will be running at 8Gb. it will be OK when writing to the tape. however, when reading from the tape (restore, verification, duplication etc...) you are likely to run into the problems, especially if these ports are on the different switches and use ISL inbetween, or your switch is multi-ASIC and the devices are connected to different ASICs. i'd advise you turn on the bottleneck detection and monitor.
01-17-2014 02:25 AM - edited 01-17-2014 02:27 AM
From stated server to tape you'll get 4Gbps as the HBA is the limiting factor on bandwith.
Not that it really matters because the fasted tapedrives LTO6/T10000D are currently unable to fully utilize that BW at sustained rates.
LTO6 does 160MB/s > roughly 1.6Gbps
T10KD does 250 MB/s > roughly 2.5Gbps
Best practice means to do whatever is necessarry to keep tapedrives in streaming mode.
If tapedrives start to "shoeshine" you'll introduce additional wear on drive mechanisms, heads and tapecartridge itself.
01-17-2014 05:24 AM - edited 01-17-2014 05:40 AM
the command is
bottleneckmon --enable -alert
but before you execute the command, have a look at the help and/or doku for bottleneckmon.
if your switch or director is a older one, perma running bottleneckmon, can lead to traffic disruption.