SAS Ultrium 920 LTO-3 Performance problem

[sdrake48]

Unable to achieve anything near the 432GB/hour published performance for this drive. In actual use, maximum performance is less than a third of that. HP DPE backup of 9.63GB takes 4m14s (136GB/hr), verify takes 5m35s.
ML370 G6, p410i/512k 6x146Gb 15k 6g RAID0, tape attached via SC44Ge. OS is SLES10 SP3 x86. 6GB (3x2GB RDIMM - one in each channel) DDR3 memory.

LTT and hptapeperf can be tweeked to get the desired numbers, but these tests do not include the disk subsystem (LTT disk subsystem perf test yields 200MM/sec). So even when disk susbsystem, memory, and tape drive are all 'capable' the expected results are not achieved. Is this a HP DPE problem, or are these results expected?

[Marino Meloni_1]

Hi
You expect to reach 432 GB/H that is 120 MB/s
You can reach 136 GB/H that is 37 MB/s

can you attach here the file result log *(in the directory log in the ltt installation path) after you run:
the device performance test
the sys performance test

(not sure what you indicate with the 200MM/s, could it be you indicate 200MB/s reading your usual data with sys perf test?


in order to have a good overview, be sure to run the tests for at least 15 minutes, that will get rid of false result due to buffers, cache etc..

When you run the sys perf test, (the backup test, not the restore one) be sure to select the same data as your compared backup, not only the speed of the disk subsystem may impact the troughput, but also the kind of data, defragmentation, open files, etc.....