why is it useful to seperate different i/o pattersn? such as multi-block reads and single block reads? > > From: "Nuno Souto" <[EMAIL PROTECTED]> > Date: 2003/07/15 Tue AM 11:59:23 EDT > To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> > Subject: Re: should you seperate indexes from tables in seperate datafiles > > ----- Original Message ----- > > > I must say that I haven't actually seen the benefits myself but my faith > > is rock solid and I'll continue to separate data from indexes. > > Don't want to debate faith... However, the technical side I can. ;) > > The practice of separating indexes and tables into individual > tablespaces comes from very early in the history of databases, > as many here know. It made sense then in terms of performance, > when databases were relatively small and the number of objects > and users in a database was also small. Besides, in those days > disks were discrete and controllers controlled each disk > separately. It was easy to separate loads, for those who > could be bothered and knew the arcane arts of disk partitioning > and file system creation. > > Nowadays with databases of thousands of tables and indexes, > with disk farms and multiple disk strings and monster > caches and disk arrays and logical volume managers, it makes > no sense whatsoever to separate tables from indexes > *FROM THE PURE PERFORMANCE POINT OF VIEW*. > > However from the maintenance and management point of view, > it makes a lot of sense. If you ever want to separate > indexes to a different disk, it's infinitely easier to > just move a set of datafiles making up a tablespace than > to have to create tablespaces, move indexes, blah blah. > In addition indexes tend to have different allocation patterns > than tables, even in LMT. It makes sense to separate them > from that point of view. > > There is another consideration which you brushed on: > You normally don't want to mix the type of I/O for indexes > (small, discrete blocks) from the potential "stringed" reads > of a full table scan. They have different characteristics > and cause all sorts of different I/O prioritization at controller > and cache level. As such, they should not reside in the same > logical device. This means in effect: not the same tablespace. > Having said that, all sorts of tricks are possible at LVM level > to avoid this even in single tablespace or single file system. > > But once again: this is all very relative and highly dependent > on the type of database and its use, type of hardware, etc. > > Bottom line: separate if you feel comfortable doing so. You do > NOT have to move the separate tablespaces into different disk > devices: it all depends on I/O patterns, configuration, load > management and so on. Analyze I/O patterns and loads, find > the bottleneck (if there is one!) and solve it. > > Do not do things just because someone says they "should/should not > be done". And that includes the above. ;) > > Try and apply a "one size fits all" policy to your work and > sooner or later you'll be replaced by a program or outsourced. > You are a DBA: think. > > Cheers > Nuno Souto > [EMAIL PROTECTED] > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Nuno Souto > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > >
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: <[EMAIL PROTECTED] INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
