Amir, Obviously, you need more cache :). (ducking and running) It might be that you're saturated at the controller (FCHBAs - host bus adapter(s)) or in internal bandwidth - depends upon the number of paths allocated to your mount points. Paul On Wed, 15 Dec 2004 20:34:40 -0000, Barr, Stephen <Stephen.Barr@xxxxxxxxx> wrote: > Hi Amir, > We also have a DMX 3000 box and have it striped 8 ways. > > We have 83 meta devices, each meta device is ~67Gb is size and is > made of eight 8.43Gb volumes. Each volume is RAID 1, however, each meta > volume is striped across it's eight individual volumes with a stripe size of > 0.94Mb. > > The issue we have at present is that we are a datawarehouse doing > lots of 1Mb direct path reads. Each read will hit 8 physical devices (with > 1Mb stripe unit size at OS). I assuming this is a bad thing - surely each of > our reads should be hitting only a single device? i.e. we're waiting on 8 > devices instead of only one. > > I've performed a number of tests with PQ on the current setup, and > it looks like the IO subsystem is saturated with a single PQ query (degree > 4) to such an extent that two PQ queries running together BOTH take twice as > long to complete....surely this isn't the pattern we should be seeing? It > essentially means that the system is 100% non-scalable. > > 1 query PARALLEL 4 (FTS) > > 1Mb Stripe unit 5 mins 18 secs > 512k Stripe unit 5 mins 18 secs > 128k Stripe unit 5 mins 52 secs > CONCAT 5 mins 10 secs > > 2 queries hitting same table PARALLEL 4 (FTS) > > 1Mb Stripe unit 8 mins 43 secs (each) > 512k Stripe unit 10 mins 12 secs (each) > 128k Stripe unit 8 mins 35 secs (each) > CONCAT 8 mins 10 secs (each) > > Does anyone have any experience of setting up this type of storage solution > for a data warehouse? > > Thanks, > > Steve. -- //www.freelists.org/webpage/oracle-l