RE: Fragmentation and RAID 1+0?

>===== Original Message From duffybj1@my-deja.com ===== >Hi all, > >I am going to be exporting and importing a table in order to get rid of >an extrodinary number of extents in the table. (>213) I figure as part >of this project, I might as well fragment the table as well to squeeze >some more performance out of the database. The table is a very busy >one, and contains approx. 3GB data (growing fast too) The hardware is a >4-way Sun E4000 with 2gb RAM and has at least 250GB of space available. >In the next 3 months I will be doing this to about 8-10 other tables as >well. > >I seek advice about how to plan this effectively. Is it better to use >Veritas to stripe and mirror the disks? Or is fragmentating the tables >and mirroring a better option? Or both? > >On this newsgroup, I have seen some posts indicating that RAID 10 and >fragmentation is better, but I don't really get why yet. With >fragmentation and striping, aren't you in effect striping twice? > > >Thanks! > >Duff > > >Sent via Deja.com http://www.deja.com/ >Before you buy. Striping your disks helps spread the work across the disks when accessing data. Fragmentation allows you to have multiple threads processing the data, as well as allowing the query processor to eliminate fragments from the query if possible. So the benefit of fragmentation would be parallel scanning of data, as well as in some case, less data must be scanned. Example of fragment elimination. I have a fragmentation strategy on if a=1 fragment 1 if a=2 fragment 2 if a=3 fragment 3 If I query where a=3 then only the fragment with a=3 gets scanned If PDQ is on and I query where b=4, the database can process all three fragments at once. parallelizing the data access for the query. I hope this helps, Will ------------------------------------------------------------ This e-mail has been sent to you courtesy of OperaMail, as a free service from Opera Software, makers of the award-winning Web Browser, Opera. Visit us at http://www.opera.com/ or our portal at: http://www.myopera.com/ Your free e-mail account is waiting at: http://www.operamail.com/ ------------------------------------------------------------