I do not doubt it. The situation you describe would be an unusual case
where most of the aggregates on the tape had only one unexpired file in
them. Thus, the tape would be 90% utilized (all those aggregates) but
90% reclaimable (because the aggregates themselves have vacancies).
In the old days, each file on client disk would correspond to a file on
tape. With small files, this is wasteful of tape space. So, ADSM puts
a bunch of client files together into one file (called the "aggregate")
for the tape. What the tape physical utilization sees is the size of
the aggregates. The logical utilization sees the size of the unexpired
files.
Rich
At 06:03 PM 10/11/99 +0200, you wrote:
>Rich,
>
>> BUT, I think that a tape will contain many aggregates,
> ... might ...
>
>> AND, I think that the physical occupancy will go down when all the files of
>> a particular aggregate are expired, even though other aggregates still
>> have files in them.
>True. But it happend to me to see volumes with 90% reclamation and
>90% utilization at the same time. When reclaimed they turned up to have
>only 10% of valid data.
>
>Mauro, STM
>
>> At 07:35 AM 10/11/99 -0500, you wrote:
>> >Betsy,
>> >
>> >Picture how much space an aggregate takes up on a physical tape at time of
>> >backup.
>> >
>> >(An aggregate being a collection of files).
>> >
>> > As files (data) expires within that aggregate the logical occupancy
>> >decreases, however the physical space occupied by the aggregate is the
same,
>> >until the tape is reclaimed. Once it is reclaimed the aggregate is then
>> >rebuilt and logical and physical occupany should be pretty much the same.
>> >
>> >At least that's the way it appears to me...
>> >
>> >Nathan
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: Moir,Betsy [SMTP:betsy.moir AT ABBOTT DOT COM]
>> > Sent: Friday, October 08, 1999 8:04 PM
>> > To: ADSM-L AT VM.MARIST DOT EDU
>> > Subject: Re: Occupancy?
>> >
>> > So, after reading that, I can understand why the question was
asked.
>> >That
>> > didn't clear up anything. Is a logical file the space defined for
>> >storing a
>> > file and a physical file the actual physical space being used for
>> >that file?
>> >
>> >
>> >
>> >
>> > ADSM-L AT VM.MARIST DOT EDU on 10/08/99 10:31:15 AM
>> > Please respond to ADSM-L AT VM.MARIST DOT EDU @ INTERNET
>> > To: ADSM-L AT VM.MARIST DOT EDU @ INTERNET
>> > cc:
>> > Subject: Re: Occupancy?
>> >
>> > Wanda:
>> >
>> > The following definitions are taken from the Glossary
>> > of the ADSM V3R1 Sun Solaris Admin Reference:
>> >
>> > logical occupancy. The space required for the storage
>> > of logical files in a storage pool. Because logical occu-pancy
>> > does not include the unused space created when
>> > logical files are deleted from aggregates, it may be less
>> > than physical occupancy. See also physical file and
>> > logical file.
>> >
>> > logical file. A client file stored in one or more server
>> > storage pools, either by itself or as part of an aggregate
>> > file. See also aggregate file and physical file.
>> >
>> > physical file. A file, stored in one or more storage
>> > pools, consisting of either a single logical file, or a group
>> > of logical files packaged together (an aggregate file).
>> > See also aggregate file and logical file.
>> >
>> > physical occupancy. The occupancy of physical files
>> > in a storage pool. This is the actual space required for
>> > the storage of physical files, including the unused space
>> > created when logical files are deleted from aggregates.
>> > See also physical file, logical file, and logical occupancy.
>> >
>> >
>> >
>> >
>> > At 10:41 AM 10/8/99 -0400, you wrote:
>> > >In the OCCUPANCY SQL table there are two columns named
>> >"physical_MB" and
>> > >"logical_MB".
>> > >Can sombody tell me the difference?
>> > >
>> > >Thanks.
>> > >
>> >
>> >>************************************************************************
>> > >Wanda Prather
>> > >The Johns Hopkins Applied Physics Lab
>> > >443-778-8769
>> > >wanda_prather AT jhuapl DOT edu
>> > >
>> > >"Intelligence has much less practical application than you'd
think"
>> >-
>> > >Scott Adams/Dilbert
>> >
>> >>************************************************************************
>> > >
>> > >
>> >
>> > Richard C. Dempsey email: dempsey AT kodak DOT com
>> > Public Online Services pager: 716-975-3539
>> > 11th Floor, Bldg 83, RL phone: 716-477-3457
>> > Eastman Kodak Company fax: 716-722-3885
>> > Rochester, NY 14650-2203
>> >
>> >
>>
>> Richard C. Dempsey email: dempsey AT kodak DOT com
>> Public Online Services pager: 716-975-3539
>> 11th Floor, Bldg 83, RL phone: 716-477-3457
>> Eastman Kodak Company fax: 716-722-3885
>> Rochester, NY 14650-2203
>
>
>
Richard C. Dempsey email: dempsey AT kodak DOT com
Public Online Services pager: 716-975-3539
11th Floor, Bldg 83, RL phone: 716-477-3457
Eastman Kodak Company fax: 716-722-3885
Rochester, NY 14650-2203
|
