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 <st...@stevenharris.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 >
