Re: IDS 10 disk configuration

Murray Wood (IList) schrieb: > Neil > > All the events that take place at a checkpoint, including waiting for all > critical processes to get out of critical and cleaning BUFFERS, need to take > place. Then, if you have 10 times as many dirty BUFFERS in a chunk then > this component of a checkpoint (page cleaner) will take longer - probably > less than 10 times as long. > > Are you running Fuzzy checkpoints? This will help speed checkpoints as will > having the MAX DIRTY set lower (it is a FLOAT variable). Also have > sufficient Cleaners, one for each chunk. Confirm your dirty buffers with > onstat -R.> Still the I/O for cleaning the LRU buffers during checkpoint is by far more efficient than LRU writes. One has to find the balance longer checkpoints and less I/O from LRU writes between 2 checkpoints versus shorter checkpoints and (much?) more write-I/O from LRU writes all the time. If you issue 'onstat -R | tail' a few seconds before a checkpoint takes place you get the picture of how much there is to do for the CLEANERS Of course CLEANERS at least equal to LRUS is a must. For those using onmode -B, CLEANERS > LRUS is a must.(look into onstat -F and see the 'C' flagged cleaners additional to one 'F' flagged cleaner per LRU, if it comes heavy) These findings are the only reason why it can be useful to have less than 128 / 512 LRUS. If you do not have 512 LUNs configured to you systems and have 512 CLEANERS at the same time starting I/O you can watch nice but unwanted I/O queueing :) dic_k -- Richard Kofler SOLID STATE EDV Dienstleistungen GmbH Vienna/Austria/Europe