ADSM-L

Re: reclamation of off-site volumes

2000-03-16 10:54:12
Subject: Re: reclamation of off-site volumes
From: "Marian L. Dalton" <marian.dalton AT CMPCO DOT COM>
Date: Thu, 16 Mar 2000 10:54:12 -0500
   I have found that quite regularly the first time through a reclaim process
for offsite volumes a small percentage of them will not be completely reclaimed.
If you look at the percentage used on  the remaining volumes, it will most
likely be quite small. In our case, I don't reset the threshold back to 100 for
several hours (we do reclaims on the weekend), so after the first process
completes another one will kick off  (the hourly process Gary referred to) . At
that point those volumes remaining will be reprocessed. I've even had at least
one occurance where a single volume had to go through three times to get it
cleared. I don't know the internals of why this happens, I just know that it
does.

   Marian Dalton
   Storage Administrator
   Central Maine Power

Gary Ison wrote:

> Eric,
>
>         I am not by any means sure of my understanding either but here goes.
>
> Reclamation is an internal, "hidden", process which is triggered
> automatically on an hourly cycle.  Apparently, it is internally limited to
> only a single driving process (the hidden part) that controls multiple
> execution processes, which are what you see with the process query.  It
> examines the volumes table entries for candidates which qualify under the
> reclaim threshold.  Those qualifying volumes, regardless of storage pool,
> are processed for reclamation.  When you adjust the threshold (at 10:00) to
> lower the value to your recovery point on the storage pool(s), it also
> triggers the "hidden" process.  The reclamation then proceeds until it
> either processes all the qualifying entries or the threshold is reset.  When
> you reset the threshold at 16:00, you effectively stop reclamation until the
> next reset at 10:00 the next day (or cycle).  The process then repeats
> itself.  The threshold reset acts as a "cancel process" command to the
> hidden reclamation driving process.
>
>         Does this make sense?
>
>         Gary L. Ison
>         Governor's Office for Technology
>         101 Cold Harbor Drive
>         Frankfort, Ky.   40601
>         Phone:  (502) 564-8724
>             Fax:  (502) 564-6856
> E-mail: Gary.Ison AT mail.state.ky DOT us <mailto:Gary.Ison AT mail.state.ky 
> DOT us>
>
> -----Original Message-----
> From:   Eric Winters
> Sent:   Wednesday, March 15, 2000 11:54 PM
> To:     ADSM-L AT VM.MARIST DOT EDU
> Subject:        Re: reclamation of off-site volumes
>
> My experience of the reclamation of off-site volumes doesn't quite match up
> with my understanding of how it should work. Perhaps someone can shed some
> light on what's really going on.
>
> I'm starting reclamation at 10:00 by reducing the reclaim value from 100 to
> 50.
> I run the following select statement to determine how many volumes are
> eligible for reclamation at this time.
>
> select count(volume_name) as "Number of vols" ,stgpool_name from volumes
> where pct_reclaim>50
> group by stgpool_name'
>
> For my offsite pool I see there are 30  volumes which are truly offsite
> which are eligible (and I also prepare a list of their volume_names).
>
> (My expectation at this point is that a single process will run which will
> reclaim ALL eligible volumes)
>
> Time passes and at 16:00 the reclaim value is reset to 100. The reclaim
> process faithfully continues its work which is to be expected. When it
> finishes 3 hours later I expect to see that there are no eligible volumes
> left. But in fact there are 8 eligible volumes (ie reclaim>50) which were
> present in my morning list. The process has finished without reclaiming all
> eligible volumes. And it wasn't cancelled.
>
> Can anyone help explain what's going on here?
>
> Regards,
>
> Eric Winters
>
> Joe Faracchio <brother AT SOCRATES.BERKELEY DOT EDU> on 14/03/2000 11:19:24
>
> Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
>
> To:   ADSM-L AT VM.MARIST DOT EDU
> cc:    (bcc: Eric Winters/Australia/Contr/IBM)
> Subject:  Re: reclamation of off-site volumes
>
> The behaviour I've seen says that it can go for a longer time than just
> 9-5 if you set the number too low or too "into" the chain. Especially if
> the number chosen is not the tape with the most to be reclaimed.
>
> I do :
>
>    select volume_name,pct_reclaim,status,pct_utilized -
>    from volumes where stgpool_name='COPYPOOL' -
>    and pct_reclaim>$1 -
>    order by pct_reclaim desc
>
> where $1 is some number like 20 or 30  and then 'dive in' about 10 down.
> The logic in ADSM causes all tapes down to this number to be reclamated
> simultaneously.  If you TAPEPOOL is collocated then the offsite
> reclamation should be more efficient read each onsite tape once to
> reclamate the offsite information.
>
>      joe.f.
>
> Joseph A Faracchio, Systems Programmer, UC Berkeley
> I
>
> On Mon, 13 Mar 2000, Walter, Jeannine wrote:
>
> > This is one of those duh questions but here goes anyway.
> > I want to run reclamation of our off-site tapes during the day from 9AM
> > until 4PM.  How do I do this?  By a script that runs as an admin
> schedule?
> > Anyone have a script they can share?
> > Thanks.
> >
> > Regards,
> > Jeannine Walter
> >
> > Purina Mills, Inc.
> > St. Louis, MO
> > 314-768-4181
> > Jeannine_Walter AT Purina-Mills DOT com <mailto:Jeannine_Walter AT 
> > Purina-Mills DOT com
> >
> >
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