How to increase IO for operation "SELECT"?

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I use windows server 2008r2 with role Hyper-V. The guest system is Ubuntu 12.04 LTC (64 bit). It is situated on the dynamic virtual hard disk /dev/sda.

There is postgresql-9.1 (amd64) on the Ubuntu 12.04. There is the database (the database size is 400 GB) on the /dev/sdb

hdparm shows: IO=150MB/s

On the picture you can see that "postgresql" uses 97% of IO, but it is only 5 MB/s. But hdparm shows that IO for /dev/sdb is 150 MB/s

How can I use hard disk on 100%? Detail you can see in the question https://serverfault.com/questions/558852/postgresql-9-1-amd64-configuration-only-for-database-search-400gb-database

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AmShegar

Posted 2013-12-04T13:01:41.093

Reputation: 123

Wild guess: you're using a magnetic hard drive (not SSD) and most time is spent on seeking the drive. Without knowing how your DB structure is set up (including indexes) and what your query is, it's difficult to say. – nitro2k01 – 2013-12-04T13:07:58.610

2>

  • don't virtualize DBs. they don;t like it unless the DBMS and VM have been tuned to work together, usually by the manufacturer. 2) SQL commands are MUCH MUCH more than simple disk IO. since IO is traditionally the slowest operation a computer can perform, your db access speed will scale much better by putting the weight of the operation elsewhere (IO needs memory to cache in, which makes minimal IO absolutely key to a scalable DBMS). I'm thinking you are barking up the wrong tree.
    • < – Frank Thomas – 2013-12-04T13:08:40.807

    My question is: IO is 150 MB/s. On the picture you can see 4 processes "postgresql". One of this processes uses only 5 MB/s (97%). I think it is problem. How can I change postgresql.conf, that this process will use 100 MB/s? Is it real? – AmShegar – 2013-12-04T13:21:32.727

    Moreover, there are another 5 virtual machines on this disk. They are running. Is it important for IO? all vitual machines and vhd disks are situated on one disk. – AmShegar – 2013-12-04T13:25:49.730

    No answers

    Asked: 2013-12-04T13:01:41.093

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    Active: 2013-12-04T13:01:41.093