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AW: [HACKERS] Some notes on optimizer cost estimates - Mailing list pgsql-hackers

From Zeugswetter Andreas SB
Subject AW: [HACKERS] Some notes on optimizer cost estimates
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Msg-id 219F68D65015D011A8E000006F8590C603FDC214@sdexcsrv1.f000.d0188.sd.spardat.at
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> As best I can measure on my hardware, the cost of a nonsequential
> disk read should be estimated at 4 to 5 times the cost of a sequential
> one --- 

Same experience here with RS6000 AIX hardware. 
450k/s random versus 4Mb/s sequential (16kb block readahead)
Compared with 256kb readahead the factor is even worse. 
Like 10Mb/s sequential.

Andreas

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