Thanks for your interest Mike.  The san guy tells me it's 380 microseconds
which equates to 76 km distance.

Regards

Steve
On 30 Oct 2014 23:50, "Ryder, Michael S" <michael_s.ryder AT roche DOT com> 
wrote:

> Steve:
>
> What is the latency on your intersite connection?
>
> Best regards,
>
> Mike, x7942
> RMD IT Client Services
>
> On Thu, Oct 30, 2014 at 8:35 AM, Steven Harris <steve AT stevenharris DOT 
> info>
> wrote:
>
> > Hi All
> >
> > I have a TSM 6.3.4 server on newish P7 hardware and AIX V7.1. HBAs are
> > all 8Gb.  The sans behind it are 8Gb or 4Gb depending which path they
> > take as we are in the middle of a SAN upgrade and there is still an old
> > switch in the mix.
> >
> > Disk is XIV behind SVC.  Tape is TS3500 and LTO5.
> >
> > According to the LTO wikipedia entry I should be able to get 140MB/sec
> > raw out of the drive.  I have an internal company document that suggests
> > sustained 210MB/sec (compressed) is attainable in the real world.
> >
> > So far my server backs up 500GB per night of DB2 and Oracle databases on
> > to file pools, without deduplication.  Housekeeping then does a
> > single-streamed simultaneous migrate and copy to onsite and offsite
> > tapes.  Inter site bandwidth is 4Gb and I have most of that to myself.
> >
> > That process takes over 5 hours so I'm seeing less than 100MB/sec.
> >
> > Accordingly I started a tuning exercise.  I copied 50GB of my filepool
> > twice to give me a test dataset and started testing, of course when
> > there was no other activity on the TSM box.
> >
> > The data comes off disk at 500MB/sec to /dev/null, so that is not a
> > bottleneck.
> >
> > Copying using dd to tape runs at a peak of 120MB/sec with periods of
> > much lower than that, as measured using nmon's fc stats on the HBAs. I
> > presume some of that slowdown is where the tape reaches its end and has
> > to reverse direction.
> >
> > Elapsed time for 100GB is 18 min, with little variation so average speed
> > is 95MB/sec
> >
> > dd ibs and obs values were varied and ibs=256K obs=1024K seems to give
> > the best result.
> >
> > Elapsed time is very consistent.
> >
> > Copying to a local drive on the same switch blade as the tape HBA or
> > copying across blades made no difference.
> >
> > Copying to a drive at the remote site increased elapsed time by 2
> > minutes, as one would expect with more switches in the path and a longer
> > turnaround time.
> >
> > Tape to tape copy was not noticeably different to disk to tape.
> >
> > Reading from tape to /dev/null was no different.
> >
> > In all cases CPU time was about half of the elapsed time.
> >
> > lsattr on the drives shows that compression is on (this is also the
> > default)
> >
> > The tape FC adapters are set to use the large transfer size.
> >
> > The test was also run using 64KB pages and svmon was used to verify the
> > setting was effective. Again no difference.
> >
> > I'm running out of ideas here.  num_cmd_elements on the hbas is 500 (the
> > default)  I'm thinking of increasing that to 2000, but it will require
> > an outage and hence change control.
> >
> > Does anyone have any ideas, references I could look at or practical
> > advice as to how to get this to perform?
> >
> > Thanks
> >
> > Steve
> >
> > Steven Harris
> > TSM Admin
> > Canberra Australia
> >
>