Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!drn.maxwell.syr.edu!news.maxwell.syr.edu!news-south.connect.com.au!news1.optus.net.au!optus!news.uwa.edu.au!nntp.waia.asn.au!203.59.27.186.MISMATCH!newsfeed.iinet.net.au!newsfeed.iinet.net.au!per-qv1-newsstorage1.iinet.net.au!per-qv1-newsstorage1.iinet.net.au!per-qv1-newsreader-01.iinet.net.au!not-for-mail Message-ID: <43297223.D8E@yahoo.com> Date: Thu, 15 Sep 2005 21:07:47 +0800 From: Connor McDonald Reply-To: connor_mcdonald@yahoo.com X-Mailer: Mozilla 3.01 (WinNT; I) MIME-Version: 1.0 Newsgroups: comp.databases.oracle.server Subject: Re: CBO influences References: <1126283179.991124.138480@z14g2000cwz.googlegroups.com> <1126284892.947680.217710@g44g2000cwa.googlegroups.com> <1126294364.813025.287860@o13g2000cwo.googlegroups.com> <1126306293.634107@yasure> <1126329859.958172@yasure> <1126374364.66827@yasure> <43282C72.36FC@yahoo.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 53 NNTP-Posting-Host: 203.59.118.201 X-Trace: 1126789664 per-qv1-newsreader-01.iinet.net.au 12705 203.59.118.201 Xref: dp-news.maxwell.syr.edu comp.databases.oracle.server:251592 Jonathan Lewis wrote: > > "Connor McDonald" wrote in message > news:43282C72.36FC@yahoo.com... > > > > In terms of mreadtim < sreadtim, we've encountered this on all databases > > at our current site that SAN attached as opposed to JBOD. Haven't > > really got the access to determine whether the SAN is *truly* yielding > > better multiread IO times than singleread IO, but ultimately we've > > resorted to > > > > - collecting system stats > > - tweaking mread to just above sread to enable mbrc inclusion for the cbo > > > > That is an interesting tell-tale about what SANs > are probably good at, and bad at, doesn't it. > > Don't share a SAN if you want to run a high > performance OLTP system - they're not very > good for small, highly randomised I/Os. > > -- > Regards > > Jonathan Lewis > > http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html > Cost Based Oracle - Volume 1: Fundamentals > On-shelf date: Nov 2005 > > http://www.jlcomp.demon.co.uk/faq/ind_faq.html > The Co-operative Oracle Users' FAQ > > http://www.jlcomp.demon.co.uk/appearances.html > Public Appearances - schedule updated 4th Sept 2005 I would generalise to SAN's are not good at IO... period :-) -- Connor McDonald Co-author: "Mastering Oracle PL/SQL - Practical Solutions" Co-author: "Oracle Insight - Tales of the OakTable" web: http://www.oracledba.co.uk web: http://www.oaktable.net email: connor_mcdonald@yahoo.com "Semper in excremento, sole profundum qui variat." ------------------------------------------------------------