ADSM-L

Re: [ADSM-L] hypothetical situation with dedup turned on

2012-11-16 12:06:02
Subject: Re: [ADSM-L] hypothetical situation with dedup turned on
From: Ray Carlson <rlcarlson AT ANL DOT GOV>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Fri, 16 Nov 2012 10:49:32 -0600
FYI - We had all the normal settings and still lost our source dedupe data 
while running 6.3.0 to 6.3.1, and no TSM was not smart enough to figure out it 
was gone and back up a fresh copy.  We are currently at 6.3.2.7.  It was one of 
the 6.3.2.x updates, released around 10/1/2012, that finally fixed the problem, 
so that we don't appear to have lost any more source data since then.  So make 
sure you are running one of the latest releases of TSM.
Ray

On Nov 16, 2012, at 9:51 AM, "Prather, Wanda" <Wanda.Prather AT ICFI DOT COM> 
wrote:

> I can confirm that if you do audit volume fix=yes , then a MOVE DATA, that it 
> LOOKS like it works.  
> The issue you mention below hadn't occurred to me. 
> Ick.  Could turn ME into a vodka drinker..
> But believe me, I"ve got "deduprequiresbackup yes" in place, and back up to a 
> non-deduped copy pool.
> 
> (And, by the way, the term "full incremental" makes me twitch, even without 
> the vodka!)
> 
> 
> 
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf 
> Of Alex Paschal
> Sent: Friday, November 16, 2012 1:09 AM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: [ADSM-L] hypothetical situation with dedup turned on
> 
> Hi, David.  You can still do as you're already doing:  "audit volume fix=yes" 
> to find the damaged blocks, then do a "move data" against the good data.  
> That would leave the unreadable data on the volume.
> 
> If the copypool volume is unavailable for a "restore volume", then the only 
> thing you could do is "delete volume discarddata=yes" and take the 
> concomitant loss of data that refers to the bad blocks. TSM should then 
> re-back up that data during the next full incremental backup.  (Full 
> incremental?  Oxymoron!  Also, maybe too much vodka. Stoli's Orange, tonight. 
>  ;-)
> 
> Question for the IBMers:  Is TSM smart enough to delete all of the file 
> objects that refer to the deduped/damaged/discarded blocks?  I would expect 
> so, especially with the ~new DB2 referential integrity enforcement, but I 
> think that's exactly what David's question is getting at.  Could we get an 
> authoritative answer on that?
> 
> And a more egg-head question from me:  if a few damaged blocks are inside an 
> aggregate, my understanding is that the entire aggregate would be marked bad 
> during the audit, which means TSM wouldn't be able to move data 
> reconstruct=yes, which would cause a larger footprint of data loss.  Is my 
> hypothesis correct?
> 
> Hmm.  Now that I think about it, CRC would have to be enabled on the stgpool 
> to detect those few bad blocks within an aggregate, otherwise the 
> headers/magic numbers for the aggregate/blocks would still be readable/good 
> and the aggregate would audit as intact. Thoughts?
> 
> Another question:  do file volumes get magic numbers?  Haha  (Sorry, I blame 
> the vodka.)
> 
> 
> On 11/15/2012 12:58 PM, Tyree, David wrote:
>> This a hypothetical situation.
>> 
>> In this situation the needed tape from the copy pool is not available.
>> I realize that the data would be lost but how what you do next?
>> 
>> if we were still running v5 of TSM we would do a move data (MOVE VOL XXX) to 
>> save what we could then delete the volume (DEL VOL XXX). We would lose some 
>> data but the next backup cycle would rebackup any missing active data.
>> 
>> Since we are now running v6 with dedup it seems like the process would be 
>> different. Each volume no longer contains a complete set of files. They now 
>> contain parts of files.
>> 
>> 
>> David Tyree
>> Interface Analyst
>> South Georgia Medical Center
>> 229.333.1155
>> 
>> -----Original Message-----
>> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf 
>> Of Grigori Solonovitch
>> Sent: Thursday, November 15, 2012 2:58 PM
>> To: ADSM-L AT VM.MARIST DOT EDU
>> Subject: Re: [ADSM-L] hypothetical situation with dedup turned on
>> 
>> Have you tried to use standard copy pol to recover any problems in primary 
>> pool?
>> 
>> Grigori G. Solonovitch
>> Senior Technical Architect  Ahli United Bank Kuwait  
>> www.ahliunited.com.kw
>> 
>> Please consider the environment before printing this E-mail
>> 
>> 
>> -----Original Message-----
>> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf 
>> Of Tyree, David
>> Sent: Wednesday, November 14, 2012 10:36 PM
>> To: ADSM-L AT VM.MARIST DOT EDU
>> Subject: [ADSM-L] hypothetical situation with dedup turned on
>> 
>>                 I've had some sys admins ask me about a possible situation 
>> with using dedup on our primary storage pool. We are currently using dedup 
>> and I can't come up with a good answer.
>>                 Ok, our primary storage pool is using dedup. Something 
>> (corruption, whatever) happens to one of the files in the primary pool and 
>> the data needed to recover the file in the primary pool is not available.
>>                 I attempt to do a restore of the corrupt  file and the 
>> needed tape is not available.
>>                 How would I go about fixing that kind of a situation?
>>                 Back before we started using dedup we could just do a move 
>> volume to save what we could and then do a delete volume and the next backup 
>> of the server would straighten everything out. We might lose inactive copies 
>> but the next backup cycle would catch the missing active files.
>>                 With the way dedup works I'm not sure what we would do.
>>                 Any suggestions?
>> 
>> David Tyree
>> Interface Analyst
>> South Georgia Medical Center
>> 229.333.1155
>> 
>> 
>> Please consider the environment before printing this Email.
>> 
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