Re: Three drive raid set.

[Larry Bolhuis <lbolhuis@xxxxxxxxxx>]

Well the numbers here do make sense.  That is drive 52 with twice the 
capacity is getting twice the work to do as drives 54 and 55.   I would 
strongly recommend against any use of three drive raid sets in a 
production environment for this reason.  Given there are 55 drives (at 
least) in the system, there must be some other drives (#51 appears a 
candidate already) that could be moved to this raid set to allow it to 
be rebuilt as a 4 drive set.  *caution* your data is exposed during that 
rebuild because the only way to get Parity spread across 4 drives is to 
stop and re-start raid.

 - Larry

rob@xxxxxxxxx wrote:

> Anyone else out there have serious performance issues with a three drive 
> raid set?  We are.  And we even ran STRASPBAL.  IBM tried iDoctor, etc. 
> Nothing out of the ordinary.  So, their suggestion is a STRASPBAL *ENDALC 
> and then add them back in with STRASPBAL *CAPACITY.
>
> Our BP says he knows of another customer that had the same issue but just 
> ordered another drive and it was solved.  Never opened pmr with IBM.
>
> Trying to find a few "me too's", hopefully with pmr #'s, to encourage IBM 
> to look harder.
>
> We will buy more drives.  We were hoping to put it off awhile.  Boss does 
> think that getting them in before year end is a good thing though, 
> budgetwise.
>
> System ASP . . . . . . . :     3316 G
> % system ASP used  . . . :    74.9333
>
> WRKDSKSTS
>               Size    %     I/O   Request   Read  Write
> Unit  Type      (M)  Used    Rqs  Size (K)    Rqs   Rqs 
> ...
> 50  4327    52923  74.9   15.3      8.6     7.0    8.2
> 51  4327    70564  74.9   25.3      7.9    13.7   11.6
> 52  4327    61744  74.9   29.4      6.4    17.7   11.6
> 53  4327    70564  74.9  131.3      5.9    47.3   83.9
> 54  4327    35282  74.9   50.7      6.6    13.8   36.8
> 55  4327    35282  74.9   70.0      5.6    22.0   47.9
>
> The last three are the raid set in question.
>
> Rob Berendt
>  

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