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#1 (**permalink**) 02-29-2008, 02:38 AM

Hi

I am trying to design an IO subsystem for my SQL Server and for that I
need to try and predict IO activity on each table in my MSSQL
Database. My idea is to move the hottest tables into special disk
subsystem away from the less hotter tables. So far I have gathered
that we have three tables more hot than the others but I have no
feeling on ratio on how hot each is and how much activity is on the
less hotter tables. I need to predict how many disks I should assign
to each subsystem and so far....
I haven't found a reasonable way to do this.

The only way I found to see read/writes and physical read/writes is on
filelevel. but I've also managed to do a trace in sqlprofiler to get
the logical read and writes per query but since my queries are often
joins I have no way of spliting that IO between the tables included in
the join and no idea on which hit the buffer pool and which didn'nt.
Is there maybe a counter or some way that I have not found?

Any input would be greatly appriciated.

best regards & thanks
Arni Snorri

#2 (**permalink**) 02-29-2008, 02:39 AM

arnie@gormur.com (Arni Snorri Eggertsson) wrote in message news:<c8d15bfa.0404280125.6f1dadcf@posting.google. com>...
> Hi
>
> I am trying to design an IO subsystem for my SQL Server and for that I
> need to try and predict IO activity on each table in my MSSQL
> Database. My idea is to move the hottest tables into special disk
> subsystem away from the less hotter tables. So far I have gathered
> that we have three tables more hot than the others but I have no
> feeling on ratio on how hot each is and how much activity is on the
> less hotter tables. I need to predict how many disks I should assign
> to each subsystem and so far....
> I haven't found a reasonable way to do this.
>
> The only way I found to see read/writes and physical read/writes is on
> filelevel. but I've also managed to do a trace in sqlprofiler to get
> the logical read and writes per query but since my queries are often
> joins I have no way of spliting that IO between the tables included in
> the join and no idea on which hit the buffer pool and which didn'nt.
> Is there maybe a counter or some way that I have not found?
>
> Any input would be greatly appriciated.
>
> best regards & thanks
> Arni Snorri

I'm not sure if it's possible to do exactly what you want - MSSQL will
probably cache a lot of the data from the 'hot' tables anyway, so the
issue is not so much the physical disk access as how much RAM you
have, and how well MSSQL uses the cache. There are a lot of
performance monitor counters for buffer and cache management you can
use to look at this.

As for the disks, I would start by identifying how much space is
required on disk, then try to use lots of smaller disks instead of
fewer bigger ones for the 'hot' filegroups. Placing the transaction
logs on separate disks would also help, of course.

Simon

#3 (**permalink**) 02-29-2008, 02:39 AM

"Arni Snorri Eggertsson" <arnie@gormur.com> wrote in message
news:c8d15bfa.0404280125.6f1dadcf@posting.google.c om...
> Hi
>
> I am trying to design an IO subsystem for my SQL Server and for that I
> need to try and predict IO activity on each table in my MSSQL
> Database. My idea is to move the hottest tables into special disk
> subsystem away from the less hotter tables. So far I have gathered
> that we have three tables more hot than the others but I have no
> feeling on ratio on how hot each is and how much activity is on the
> less hotter tables. I need to predict how many disks I should assign
> to each subsystem and so far....
> I haven't found a reasonable way to do this.

If you don't have it, get the Microsoft Press book on SQL Server Performance
tuning. Lots of good help here.

>
> The only way I found to see read/writes and physical read/writes is on
> filelevel. but I've also managed to do a trace in sqlprofiler to get
> the logical read and writes per query but since my queries are often
> joins I have no way of spliting that IO between the tables included in
> the join and no idea on which hit the buffer pool and which didn'nt.
> Is there maybe a counter or some way that I have not found?
>
> Any input would be greatly appriciated.
>
> best regards & thanks
> Arni Snorri

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