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Thread: Amanda getting slower every version?

  1. #1

    Default Amanda getting slower every version?

    Some time ago I built an Amanda 2.5.x system on SuSE 10.3 (using the repo version) with an IBM Ultra 160 scsi LTO3 and was getting amtapetype figures of around 65000 kp/s.

    I recently built a second system on Suse 11.1, again using the repo version 2.5.2.1 on an IBM x3550 with a Quantum SAS LTO4 connected via an LSI SAS3801E. This only gave me ~45000 kp/s.

    Rebuilding the above to Suse 11.2 and the supplied 2.6.1.1-3.4 dropped this figure even more to ~37000 kp/s, a figure confirmed by a third build on a different cpu but the same other components.

    I get over 200MB/s writing through the HBA to a SAS raid, and an LTO4 should be good for 120MB/s and is audibly spending a lot of time waiting, so why the pants performance?

    Incidentally, what is the relation between the amtapetype "kp/s" and the more usual measure of throughput in MB/s? I presume it stands for kilo packets/sec but I am not sure of the packet size, its clearly not the block size.

  2. #2

    Default

    OK so I think I may be getting to the root of this.
    I have run some tests using "dd if=/RAID/randombytefile of=/dev/nst0 bs=NNNk" with varying values of NNN (the blocksize)
    NNN Throughput
    32k 44MB/s *Not too disimilar to amtapetype figure.
    128k 90MB/s
    256k 88MB/s
    512k 86MB/s

    From this it would seem that Amanda's default 32K blocksize is severely limiting the performance on more modern faster tape units.

  3. #3

    Default

    OK, So I think I have answered my own query.
    MY original build was on 2.5.2p1-1, and my build had a fixed blocksize such that changing that parameter made no difference to amtapetype. However I now find that on my build of 2.6.1.1p1 this is no longer true and after trying various figures have come up with the following amtapetype results:-

    #Z400 based system
    define tapetype quantum-lto4-256 {
    comment "Created by amtapetype; compression enabled"
    length 815598080 kbytes
    filemark 5688 kbytes
    speed 75434 kps
    blocksize 256 kbytes
    }
    #IBM x3550 system
    define tapetype quantum-lto4-256 {
    comment "Created by amtapetype; compression enabled"
    length 815319040 kbytes
    filemark 4543 kbytes
    speed 77597 kps
    blocksize 256 kbytes
    }
    Running an actual dump on the Z400 system showed TAPER STATS as going up from ~36MB/s to ~89MB/s
    Job Done

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