[gpfsug-discuss] DB2 (not DB2 PureScale) and Spectrum Scale

Jim Doherty jjdoherty at yahoo.com
Thu Jun 10 14:42:18 BST 2021


 I think I found the document you are talking about. In general I believe most of it still applies. I can make the following comments on it about Spectrum Scale: 


1 - There was an effort to simplify Spectrum Scale tuning, and tuning of worker1Threads should be replaced by tuning workerThreads instead. Setting workerThreads, will auto-tune about 20 different Spectrum Scale configuration parameters (including worker1Threads) behind the scene. 

 

2 - The Spectrum Scale pagepool parameter defaults to 1Gig now, but the most important thing is to make sure that you can fit all the IO into the pagepool. So if you have 512 threads * 1 MB you will need 1/2 Gig just to do disk IO, but if you use 4MB that becomes 512 * 4 = 2Gig just for disk IO. I would recommend setting the pagepool to 2x the size of this if you are using direct IO so 1 Gig or 4 Gig for the example sizes I just mentioned. 



3 - One consideration that is important is sizing the initial DB2 database size correctly, and when the tablespace needs to grow, make sure it grows enough to avoid constantly increasing the tablespace.

The act of growing a database throws GPFS into buffered IO which can be slower than directIO. If you need the database to grow all the time, I would avoid using direct IO and use a larger GPFS pagepool to allow it cache data. Using directIO is the better solution.

Jim Doherty

    On Monday, June 7, 2021, 11:03:26 AM EDT, Wally Dietrich <wallyd at us.ibm.com> wrote:  
 
  Hi. Is there documentation about tuning DB2 to perform well when using Spectrum Scale file systems? I'm interested in tuning both DB2 and Spectrum Scale for high performance. I'm using a stretch cluster for Disaster Recover (DR). I've found a document, but the last update was in 2013 and GPFS has changed considerably since then.
Wally Dietrichwallyd at us.ibm.com
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