Just depends on your settings... eg max phys io = 1m, db mult read * blk size = 1m
then - 64k stripe means 16 disks in the read - 128k means 8 - 512k means 2 - 1m means 1 etc Involving lots of disks in a single read tends be good for systems will small user populations (basically you're better at a given point in time there will only be 1 or 2 concurrent queries on the system and you still want to maximise IO bandwidth). As the user population gets larger, then involving lots of disks in a single read can often lead to IO "thrashing" Cheers Connor --- Jared Still <[EMAIL PROTECTED]> wrote: > > Maybe I've forgotten something fundamental about the > way > RAID 5 works, I dunno. > > But I'm having a hard time understanding how stripe > size is > going to determine the number of heads used in an > IO. > > RAID 5 distributes the data across all spindles, > with 1 or more > of the spindles for any IO being used for the parity > data. > > Someone care to enlighten me? > > Thanks, > > Jared > > On Thursday 21 November 2002 06:33, Thomas Day > wrote: > > We had a discussion about a year ago here and if I > remember correctly the > > "best" stripe size is a function of number of > concurrent users. With a > > small number of users you want a small stripe size > so that each read i/o > > will utilize the maximum number of heads. It will > also tie up the RAID > > device for the duration of the read. With a large > number of users you want > > a very large stripe size so that a minimum of > heads will be used for each > > read and the RAID device can handle multiple > requests at a time. > > > > I don't recall any specific numbers and, as you > say, the technology is > > changing so quickly that a discussion from a year > ago may not be pertinent > > to today's environment. > > > > > > > > > > "Post, Ethan" > > <Ethan.Post To: > Multiple recipients of > > list ORACLE-L <[EMAIL PROTECTED]> @ps.net> > cc: > > Sent by: root Subject: > 1M STRIPE SIZE BEST? > > > > > > 11/20/2002 > > 05:53 PM > > Please > > respond to > > ORACLE-L > > > > > > > > > > > > > > A number of papers recommend a stripe size of 1 M > (even for EMC) for > > volumes > > containing data files. I also have the following > email from Eyal Aronoff > > of > > Quest dated Nov 2000. A number of the white > papers are more recent. > > > > > ============================================================ > > The reasons for a larger stripe size on a non-RAID > 5 device are: > > 1) Sequential reads are faster if you can take > advantege of the read ahead > > built into the disk caching > > 2) If a 64K read does not start on the first block > of the stripe, two > > "spindled" are locked for the duration of the read > > > > However, lately we have been testing some EMC gear > and it looks like EMC > > have optimized both of those for smaller strip > size too. > > > > The bottom line - I no longer have an opinion one > way or another. The > > undelying technology just changes too rapidly. > > > > Eyal > > > ============================================================ > > > > Your opinions/comments as far as a "best" practice > in setting stripe sizes > > would be greatly appreciated. > > > > Thanks, > > Ethan > > -- > > Please see the official ORACLE-L FAQ: > http://www.orafaq.com > > -- > > Author: Post, Ethan > > 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.com > -- > Author: Jared Still > 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). > ===== Connor McDonald http://www.oracledba.co.uk http://www.oaktable.net "GIVE a man a fish and he will eat for a day. But TEACH him how to fish, and...he will sit in a boat and drink beer all day" __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: =?iso-8859-1?q?Connor=20McDonald?= 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).
