Обсуждение: Disk Access Question

I have a question on disk access.

How often is PostgreSQL accessing/touching the files that are on the hard drive?

What I'm trying to ask is, is PostgreSQL constantly updating access timestamps or something like that on the database files even if they are not being queried?  This questions comes from an Oracle background where Oracle was updating the individual files every 3 seconds if I am remembering correctly.

I am trying to figure out besides the queries, what sort of accessing is PostgreSQL doing to my drives so we can try and resolve some i/o issues.

Thanks,

Chris

Sorry, for got to mention pg 7.3.4.

On Tuesday 20 September 2005 13:55, Chris Hoover wrote:
> I have a question on disk access.
>
> How often is PostgreSQL accessing/touching the files that are on the hard
> drive?
>
> What I'm trying to ask is, is PostgreSQL constantly updating access
> timestamps or something like that on the database files even if they are
> not being queried? This questions comes from an Oracle background where
> Oracle was updating the individual files every 3 seconds if I am
> remembering correctly.
>
> I am trying to figure out besides the queries, what sort of accessing is
> PostgreSQL doing to my drives so we can try and resolve some i/o issues.
>

AFAIK unless your actually doing something,it wont access your data files at
all.  Note that something is pretty wide here, insert/update/vacuum/analyze
and even select will cause file access but otherwise it wont.

--
Robert Treat
Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL

Robert Treat wrote:
> On Tuesday 20 September 2005 13:55, Chris Hoover wrote:
>> I have a question on disk access.
>>
>> How often is PostgreSQL accessing/touching the files that are on the hard
>> drive?
>>
>> What I'm trying to ask is, is PostgreSQL constantly updating access
>> timestamps or something like that on the database files even if they are
>> not being queried? This questions comes from an Oracle background where
>> Oracle was updating the individual files every 3 seconds if I am
>> remembering correctly.
>>
>> I am trying to figure out besides the queries, what sort of accessing is
>> PostgreSQL doing to my drives so we can try and resolve some i/o issues.
>>
>
> AFAIK unless your actually doing something,it wont access your data files at
> all.  Note that something is pretty wide here, insert/update/vacuum/analyze
> and even select will cause file access but otherwise it wont.

You can mount your partition ( on Linux ) specifing the "noatime" option this
will avoid your inode access time to be updated when files are only read.
Postgres do not use this information so you are safe.

Regards
Gaetano Mendola