Folks, I'd truly appreciate if somebody with a moment to spare and appropriate equipment at hand would run a couple of tests as shown below and report back to the list. -- Warm regards, Michael Green
On Sat, Apr 10, 2010 at 1:47 AM, Michael Green <mishagr...@gmail.com> wrote: > I've been playing with ITDT v4 for quite some time now. I installed it > on one of my production servers which is a hefty > IBM x3850, SLES10 SP2 x64, lin_tape 1.34. The drives are LTO4. > The FC fabric is 4Gb all along from the server to the library. > > I'm getting mixed results that I cannot explain. > Using the "Full write" test from ITDT using Incompressible data and > 256K transfer rate I consistently score above 100MB/sec write rates. > At the same time using simple dd method (with compression turned off, > same drive, same cartridge) as described in Richards ADSM Quick facts > (search for THROUGHPUT MEASUREMENT topic) I score no more than > 45MB/sec. > The dd method is simple: > 1. turn drive compression off (using ITDT or tapeutil) > 2. run > # time dd if=/dev/zero of=/dev/IBMtape7 bs=256k count=40960. > (40960 by 256K is 10240MB). Now measure the time and divide 10240MB by > it. This test consistently yields ~45MB/sec in my experiments. > > TAR'ing similar amount of data in a few big files yields about > 40MB/sec. The underlying disks (a mirror of 2 146GB SAS 3Gb drives) > are well capable of providing 80MB/sec sustained. > > Anyone tried doing similar tests? Anyone bothered playing with ITDT > read/write tests at all? > -- > Warm regards, > Michael Green >