On 11/15/2011 01:25 PM, Joel.Patterson@xxxxxxxxxxx wrote: > > Someone has requested that we cost out some thing including portioning and > suggested that to get the "performance benefit out of partitioning you needed > separate physical disks". > > It would be 11.2.0.3, we use a SAN, and have a variety of RAID groups > including 10, 5, and 6. I don't expect this to ever get to that size, right > now it is about 100Gb, but size hasn't been discussed yet. (we are meeting > in the future). > > I wonder just how much data is needed to realize a cost/benefit, and other > considerations such as channels etc., and basically, is that true and > accurate? I have asked him for some supporting docs. > > I remember hearing that raw disks could give you 10% more -- until you dug a > little further and realize that you would need about a Terabyte of data to > realize such an improvement - in reality. > > Any comments or experience is appreciated, (including supporting docs if > handy). > > > Joel Patterson > Database Administrator > 904 727-2546 > > -- > //www.freelists.org/webpage/oracle-l > > > Joel, I don't think that one should first think "disks" when one think about partitioning. If you consider a table or a partition as a kind of pool of Oracle blocks, whenever you partition, somehow you redirect your inserts to a smaller pool - you are, if I dare say, lowering entropy. That means that parallel inserts may conflict more if they go to the same partition, and also that selects may perform fewer logical I/Os if there is in your query something that allows partition pruning. I am not sure that the comparison is very good, but for me it's akin to the clustering factor of indexes, primarily more a question of how rows are distributed among Oracle blocks than how Oracle blocks are stored on disk. HTH, -- Stephane Faroult RoughSea Ltd <http://www.roughsea.com> Konagora <http://www.konagora.com> RoughSea Channel on Youtube <http://www.youtube.com/user/roughsealtd> -- //www.freelists.org/webpage/oracle-l