Re: High I/O writes activity on disks causing images on browser to lag and not load

On Wed, June 3, 2009 12:59, Bill Moran wrote:
> In response to Jennifer Trey <jennifer(dot)trey(at)gmail(dot)com>:
>
>> Hmm, I just noticed the same write behavior on my Windows Xp laptop but
>> the
>> values was a little less.
>> I even created an DB with one table and column and this still happened
>> when querying it.
>
> By "created", you mean you created a table and populated it with data?
> Once you do that, do a "SELECT count(*)" on that table, then wait for
> the I/O to calm down. That select statement will force all the hint
> bits to be updated. See if subsequent selects still cause disk
> activity.
>
>> Are you sure that moving to Linux will solve this?
>
> I never advocated that Linux would fix this, and I still don't. I
> recommended a short list of methods to investigate the issue, most of
> which you ignored. You _still_ don't know what's being written, and
> I _highly_ recommend that you isolate that before doing something
> radical like switching operating systems.
>
> If you've got the DB configured in such a way that it's causing a lot of
> write ops, it's going to do it in Linux or any other Posix systems, or
> on CP/M for that matter.
>
> Posix systems have a laundry list of tools to identify what programs are
> doing. It's been a while since I've worked with Windows, but I seem to
> remember MS having tools to audit disk activity. Turn them on and see
> which files are actually being written to.
>
>> Could you please check if
>> you notice the same write behavior?
>
> My BSD-based systems to no do this. Doing a select count(*) on a table
> with 750,000 rows produces no write activity.
>
> --
> Bill Moran
> http://www.potentialtech.com
> http://people.collaborativefusion.com/~wmoran/
>
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Jennifer,

While not the "Best" solution by any stretch, you can use Windows Task
Manager (instead of Windows Performance Manager) to track the I/O writes
for each process.

Start Task Manager (run %windir%\system32\tskmgr32.exe)

On the Process Tab check the box "Show processes from all users"

Select View->Select Columns

Check the boxes related to I/O that you want to examine.

Sort the processes by "Image Name" to group PostgreSQL related processes
(again on the Process tab).

Watch your I/O counters that you selected.

Run your query (SQL Query) again. This is to determine if it is
PostgreSQL doing the disk I/O or Windows.

Again - this is a rough guesstimate. Better data can be collected by
using the SysInternals tools (available for free from the Microsoft
website) or using the performance tools in Windows to watch the "real"
disk I/O parameters.

Good Luck.

Tim
--
Timothy J. Bruce

Registered Linux User #325725
kboodu