A mixed bag of questions...

Last post 05-18-2011, 4:49 AM by cho. 6 replies.
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  • A mixed bag of questions...
    Posted: 05-08-2011, 12:40 AM

    Just a few questions that I was hoping some experienced folks could provide some feedback on.  I was pretty sure at least a few of these had been covered in length but I either couldn't find them or didn't go back far enough.  Either way, here goes...

    1) Is there any reason I should be running Regular Fulls instead of Synthetic Fulls?  I'm currently using a global dedupe policy against my storage policy and have DASH Full's and Client-Side Dedupe enabled on my primary policy copy (Simpana v9 SP2).  I know there was some discussion about pruned data in relation to Synthetics but my understanding was this was resolved (or just poorly worded in BoL).

    2) Do you guys verify every job/copy?  I'm currently doing backups to maglib, then a secondary copy to tape.  I'm assessing whether I need to verify everything or if I can trim some fat.  My thinking is if I'm verifying the tapes why verify the maglib since I already have verified data to fallback on in a pinch.

    3) I saw some brief discussion on a few reg keys that optimized read-ahead operations which drastically sped up aux copies and potentially other operations.  Was there any definitive answer on this?  The initial remarks looked very promising.

    Thanks in advance :)

    Just my 1.4 cents (after taxes)
  • Re: A mixed bag of questions...
    Posted: 05-09-2011, 7:40 AM

    1) I'd like to know too.

    2) I'd like to know too.

    3) It seems to make a massive difference.  I'm transitioning a bunch of jobs from tape as primary to d2d/dedupe and on the aux copies I'm seeing anything from around 200-300gb/hr combining 4 streams to 1 tape drive.  You certainly have nothing to lose from using that key.

  • Re: A mixed bag of questions...
    Posted: 05-09-2011, 9:21 AM

    1)    I would run a real full every once in a while just to have a "real" baseline for the subsequent syn fulls. 

    2) No reason to, and if you are verifying on the mag i dont see a reason to verify on the tape (since the copy should be the same) 

    3) Can you link to this conversation which may provide further details to what you are referencing.

  • Re: A mixed bag of questions...
    Posted: 05-09-2011, 11:43 AM

    1) That just seems kind of a cludgey way of insuring data integrity that the software should already be taking care of.  After doing some more reading I feel pretty confident I'm ok running just Synthetics based on a few peoples' experiences and also the fact I have the option "Verify Synthetic Full" enabled.  Here's a quote from the v9 BoL:

    "Use the Verify Synthetic Full advanced backup option to ensure that never-changing files are backed up. This is especially useful when synthetic full backups are used consistently to replace conventional full backups."

    Also, as I was typing this my Commvault account rep emailed me and told me his SME stated the Synthetic Fulls are fine to use exclusively.  Issues with pruned/corrupted data was related primarily to older versions using tape.

    2) Unfortunately, I definitely have to verify the tape jobs since those are my last line of defense in the event there's a fire/etc that takes out the building.  Currently though my estimations on my windows for jobs such as verification, aux copies, etc are such that I can afford to verify everything.  I was just curious if it was necessary from the maglib side since that data is essentially being verified when it's aux copied.

    3)  Here is the link to the discussion in question:


    Just my 1.4 cents (after taxes)
  • Re: A mixed bag of questions...
    Posted: 05-09-2011, 5:21 PM

    1) I too find it silly to do a real full every once in a while just in case. Synthetic fulls should be enough as it will do the exact same thing as a full (using the verify synthetic full option). If you're going to do real fulls every now and then... you might just want to backup your data with a second parallel backup software just in case one of the 2 doesn't work! The only thing I can say here is to test your restores every couple months (like you should even using real fulls anyway). Personally, I'm about to set scheduled restores at our DR site on temp storage so that our critical data's restore capabilities is automatically tested every 3 months or so.

    2) If you look at your primary storage after you've aux copied a job, you will see its verification status is set to successful since it was able to do its aux copy (hence reading all the data from it). I only do aux copies to disk but I'm guessing it will have the same behaviour aux copying to tape. Only thing you could want is to set an expiration on the verification so you verify your jobs something like 6 months later (if it's still on disk). I do a verification of all my weekly fulls at the DR site though since you only write to the destination and don't do a full read of the data. I will most likely get rid of this once I setup my automated restores procedures.

    3) So far the speed gains have been great :) I've had some aux copies that went pending with strange errors on rare occasions. I would usually disable the key, restart the job which would continue where it left off and finish without errors. Not quite sure if the random issues were actually caused by the key or not. I would have to investigate next time it happens but since it takes 2 seconds to disable, I didn't bother too much to investigate yet.

  • Re: A mixed bag of questions...
    Posted: 05-09-2011, 5:31 PM


    2) I'm thinking there's some intelligence in the software that knows this as I've had jobs on maglib that were both queued for verification and queued for aux copy to tape and when I ran a data verification it didn't bother verifying the maglib job because I guess it figured that would occur during the copy.  I'm not complaining either way as it looks like the problem is solved for me without even doing anything.

    3) Yea, that's what I was afraid of.  I kinda figured if there were huge gains to be had from enabling one reg key that the Commvault devs would do it unless there was a reason not to.  I'm getting "Ok" speed for now so I'll hold off enabling it until I get word from a dev on this, but I'm looking forward to it based on other people's experiences with it.  Two seconds isn't very long to fix something but I'm definitely a "set it and forget it" admin when I can be ;)

    Just my 1.4 cents (after taxes)
  • Re: A mixed bag of questions...
    Posted: 05-18-2011, 4:49 AM

    2) I don't  verify my copy to tape, because the RAW is very reliable.


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