DDS3 Tape drive not compressing? - HP UX

This is a discussion on DDS3 Tape drive not compressing? - HP UX ; Hi, I have a HPUX 11.11 box with a C1537A tape drive which is I believe DDSIII. Trouble is I can't see that hardware compresssion is working. Using omniback the media look like DDSIII as the capacity is about 12Gb: ...

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  1. DDS3 Tape drive not compressing?

    Hi,

    I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    DDSIII. Trouble is I can't see that hardware compresssion is working.

    Using omniback the media look like DDSIII as the capacity is about 12Gb:
    $omnimm -media_info 581490 -detail
    ....
    Total blocks : 11743616
    (or is this the compressed capacity being reported? No that doesn't make
    much sense)


    Trouble is when I write 12Gb (added up totals from bdf) it's too much -
    thus there is no compression going on it seems.

    I am using the compression device: /dev/rmt/c1t0d0BEST which should be
    the right one.

    So I am a bit stumped.

    Any clues?
    Thanks,
    Adam.



  2. Re: DDS3 Tape drive not compressing?

    Adam Skeggs wrote:
    > Hi,
    >
    > I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    > DDSIII. Trouble is I can't see that hardware compresssion is working.
    >
    > Using omniback the media look like DDSIII as the capacity is about 12Gb:
    > $omnimm -media_info 581490 -detail
    > ...
    > Total blocks : 11743616
    > (or is this the compressed capacity being reported? No that doesn't make
    > much sense)
    >
    >
    > Trouble is when I write 12Gb (added up totals from bdf) it's too much -
    > thus there is no compression going on it seems.
    >
    > I am using the compression device: /dev/rmt/c1t0d0BEST which should be
    > the right one.
    >
    > So I am a bit stumped.
    >
    > Any clues?
    > Thanks,
    > Adam.
    >
    >

    Adam,


    You do not tell us what kind of data you send to the tape. Some data
    does not compress at all, so you end up with a tape that can contain
    'only' 11GB (estimated based on your Total blocks).


    Regards,


    Jan Gerrit

  3. Re: DDS3 Tape drive not compressing?

    Adam Skeggs wrote:
    > Hi,
    >
    > I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    > DDSIII. Trouble is I can't see that hardware compresssion is working.


    Check the drive's hardware settings to see if it is not set to no
    compression. Most drives can be set to compression, no compression and
    software controlled (non) compression.

    > Using omniback the media look like DDSIII as the capacity is about 12Gb:
    > $omnimm -media_info 581490 -detail
    > ...
    > Total blocks : 11743616
    > (or is this the compressed capacity being reported? No that doesn't make
    > much sense)


    It indeed reports the uncompressed capacity.

    > Trouble is when I write 12Gb (added up totals from bdf) it's too much -
    > thus there is no compression going on it seems.


    bdf info is rather meaningless, because it does not account for the
    OmniBack 'overhead'.

    Try to create a datalist/backup_specification which would result in a
    *little* more written to the drive, preferably some 13GB. As soon as you
    can write more than 12GB, you *know* that hardware compression is
    working, because the Native Mode (is uncompressed) capacity of DDS-3 is
    12GB, i.e. anything above 12GB is compressing.

    Also make sure that you do *not* specify compression in OmniBack. In
    OmniBack, "compression" is *software* compression and software
    compression can/will conflict with hardware compression. I.e. if both
    are enabled, you will only be able to write *less* than 12GB
    (uncompressed), instead of more.

    > I am using the compression device: /dev/rmt/c1t0d0BEST which should be
    > the right one.


    Make sure that lssf(1M) actually says "best density".

    > So I am a bit stumped.
    >
    > Any clues?
    > Thanks,
    > Adam.


    If all the above does not help, you could try the ddsinfo utility from
    "The Porting and Archive Centre for HP-UX" .
    It is rather old and had some limitations. I don't now if there is
    anything newer/better somewhere.

  4. Re: DDS3 Tape drive not compressing?

    Frank Slootweg wrote:
    > Adam Skeggs wrote:
    >
    >>Hi,
    >>
    >>I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    >>DDSIII. Trouble is I can't see that hardware compresssion is working.

    >
    >
    > Check the drive's hardware settings to see if it is not set to no
    > compression. Most drives can be set to compression, no compression and
    > software controlled (non) compression.
    >
    >
    >>Using omniback the media look like DDSIII as the capacity is about 12Gb:
    >>$omnimm -media_info 581490 -detail
    >>...
    >> Total blocks : 11743616
    >>(or is this the compressed capacity being reported? No that doesn't make
    >>much sense)

    >
    >
    > It indeed reports the uncompressed capacity.
    >
    >
    >>Trouble is when I write 12Gb (added up totals from bdf) it's too much -
    >>thus there is no compression going on it seems.

    >
    >
    > bdf info is rather meaningless, because it does not account for the
    > OmniBack 'overhead'.
    >
    > Try to create a datalist/backup_specification which would result in a
    > *little* more written to the drive, preferably some 13GB. As soon as you
    > can write more than 12GB, you *know* that hardware compression is
    > working, because the Native Mode (is uncompressed) capacity of DDS-3 is
    > 12GB, i.e. anything above 12GB is compressing.
    >
    > Also make sure that you do *not* specify compression in OmniBack. In
    > OmniBack, "compression" is *software* compression and software
    > compression can/will conflict with hardware compression. I.e. if both
    > are enabled, you will only be able to write *less* than 12GB
    > (uncompressed), instead of more.
    >
    >
    >>I am using the compression device: /dev/rmt/c1t0d0BEST which should be
    >>the right one.

    >
    >
    > Make sure that lssf(1M) actually says "best density".
    >
    >
    >>So I am a bit stumped.
    >>
    >>Any clues?
    >>Thanks,
    >>Adam.

    >
    >
    > If all the above does not help, you could try the ddsinfo utility from
    > "The Porting and Archive Centre for HP-UX" .
    > It is rather old and had some limitations. I don't now if there is
    > anything newer/better somewhere.

    There is also the StorageWorks Library and Tape tools, the Windows
    versions works OK, I've never used the HPUX one. A quick search on ITRC
    did not find it, what a surprise...

  5. Re: DDS3 Tape drive not compressing?

    Alan D Johnson wrote:

    > Frank Slootweg wrote:
    >
    >> Adam Skeggs wrote:
    >>
    >>> Hi,
    >>>
    >>> I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    >>> DDSIII. Trouble is I can't see that hardware compresssion is working.

    >>
    >>
    >>
    >> Check the drive's hardware settings to see if it is not set to no
    >> compression. Most drives can be set to compression, no compression and
    >> software controlled (non) compression.
    >>
    >>
    >>> Using omniback the media look like DDSIII as the capacity is about 12Gb:
    >>> $omnimm -media_info 581490 -detail
    >>> ...
    >>> Total blocks : 11743616
    >>> (or is this the compressed capacity being reported? No that doesn't
    >>> make much sense)

    >>
    >>
    >>
    >> It indeed reports the uncompressed capacity.
    >>
    >>
    >>> Trouble is when I write 12Gb (added up totals from bdf) it's too much
    >>> - thus there is no compression going on it seems.

    >>
    >>
    >>
    >> bdf info is rather meaningless, because it does not account for the
    >> OmniBack 'overhead'.
    >>
    >> Try to create a datalist/backup_specification which would result in a
    >> *little* more written to the drive, preferably some 13GB. As soon as you
    >> can write more than 12GB, you *know* that hardware compression is
    >> working, because the Native Mode (is uncompressed) capacity of DDS-3 is
    >> 12GB, i.e. anything above 12GB is compressing.
    >>
    >> Also make sure that you do *not* specify compression in OmniBack. In
    >> OmniBack, "compression" is *software* compression and software
    >> compression can/will conflict with hardware compression. I.e. if both
    >> are enabled, you will only be able to write *less* than 12GB
    >> (uncompressed), instead of more.
    >>
    >>
    >>> I am using the compression device: /dev/rmt/c1t0d0BEST which should
    >>> be the right one.

    >>
    >>
    >>
    >> Make sure that lssf(1M) actually says "best density".
    >>
    >>
    >>> So I am a bit stumped.
    >>>
    >>> Any clues?
    >>> Thanks,
    >>> Adam.

    >>
    >>
    >>
    >> If all the above does not help, you could try the ddsinfo utility from
    >> "The Porting and Archive Centre for HP-UX" .
    >> It is rather old and had some limitations. I don't now if there is
    >> anything newer/better somewhere.

    >
    > There is also the StorageWorks Library and Tape tools, the Windows
    > versions works OK, I've never used the HPUX one. A quick search on ITRC
    > did not find it, what a surprise...

    Oops, helps if I speel rite..
    http://h18006.www1.hp.com/products/s...ltt/index.html

  6. Re: DDS3 Tape drive not compressing?

    Adam Skeggs wrote:
    > Hi,
    >
    > I have a HPUX 11.11 box with a C1537A tape drive which is I believe
    > DDSIII. Trouble is I can't see that hardware compresssion is working.
    >
    > Using omniback the media look like DDSIII as the capacity is about 12Gb:
    > $omnimm -media_info 581490 -detail
    > ...
    > Total blocks : 11743616
    > (or is this the compressed capacity being reported? No that doesn't make
    > much sense)
    >
    >
    > Trouble is when I write 12Gb (added up totals from bdf) it's too much -
    > thus there is no compression going on it seems.
    >
    > I am using the compression device: /dev/rmt/c1t0d0BEST which should be
    > the right one.
    >
    > So I am a bit stumped.
    >
    > Any clues?
    > Thanks,
    > Adam.
    >
    >


    Well now, using tar I can write about 20Gb compared to 12Gb using
    Omniback with the same device file. Need to check a bit more...

    Adam.

  7. Re: DDS3 Tape drive not compressing?

    Adam Skeggs wrote:
    [deleted]
    > Well now, using tar I can write about 20Gb compared to 12Gb using
    > Omniback with the same device file. Need to check a bit more...


    So you know that the drive *is* using hardware compression if you use
    that device file (i.e. the one you used with tar). So make sure that the
    OmniBack device definition uses the *exact same* device file (as tar)
    and, I I mentioned, check that there is *no* (software) "compression"
    enabled in OmniBack. I don't remember where the OB compression setting
    is, in the datalist (= backup specification) or in the device
    definition, so you will have to find that out for yourself.

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