why update is slower on my pc? - Mailing list pgsql-general

From sunpeng
Subject why update is slower on my pc?
Date
Msg-id AANLkTimWE18LmL859k1BKN8QKck5HsHJP+foAGashH91@mail.gmail.com
Whole thread Raw
Responses Re: why update is slower on my pc?  (Satoshi Nagayasu <satoshi.nagayasu@gmail.com>)
Re: why update is slower on my pc?  (Scott Marlowe <scott.marlowe@gmail.com>)
List pgsql-general
I use my laptop to execute the following sql, it's:
mydb=# update _mcir_2597431_clusterid2 set clusterid = 3;
UPDATE 104770
Time: 8666.447 ms

and on my pc:
mydb=# update _mcir_2597431_clusterid2 set clusterid = 3;
UPDATE 104770
Time: 27171.203 ms

First I wondered whether the write speed on pc is lower than laptop, so i use a cp command to test a write speed:
on my laptop:
postgres@postgres-laptop:~$ time cp backup/soft/data\ mining/SPSS\ Clementine\ v11.rar  develop/

real    0m19.403s
user    0m0.032s
sys    0m3.472s

on my pc:
postgres@postgres-laptop:~$ time cp backup/soft/data\ mining/SPSS\ Clementine\ v11.rar  develop/

real    0m9.192s
user    0m0.008s
sys    0m1.708s

so the writing speed on disk of pc is much faster than laptop, why the update sql command is much slower than my laptop? what's the reason causing such decrease?

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