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Re: Shared Disk Server and partitioned tables

Posted By: Cesar Inacio Martins
Date: Sunday, 22 February 2009, at 8:17 a.m.

In Response To: Shared Disk Server and partitioned tables (SCOTT ROBERTS)

Using shared disk , you can think like your system running at the same machine but with opportunity to reorder all database. But at the end you will have separeted machine process.
To do this you need start the tunning at the Storage, first you need to understand how works your storage , like: type of RAIDS , buffer cache in the Disk Control and mirror of this buffer cache.
Than , maybe, if your database modeling permits, you can separate the OLAP and OLTP between different LUNs (and separating in differ dbspaces/chunks) to avoid any performance issues affect in the cache, and disk I/O at the storage.
So, a very superficial suggestion , just configure a set of physical disks (LUNs) to OLTP and other set of physical disks to OLAP data.

César

--- Em sáb, 21/2/09, SCOTT ROBERTS <sroberts20@csc.com> escreveu:

De: SCOTT ROBERTS <sroberts20@csc.com>
Assunto: Shared Disk Server and partitioned tables [14967]
Para: ids@iiug.org
Data: Sábado, 21 de Fevereiro de 2009, 15:59

I have a 250 gig database with an ugly mix of OLTP and OLAP processes. The
ugly sales comparision queries do a HUGE amount of summing, comparing,
calculating on the fly. They are very CPU intensive. The CPU can be pegged at
100% for hours while the disk utilization is around 20 to 30%. When the ugly
sales comparision queries get heavy, the performance degrades to the point
that the OLTP users say it is unusable.

After years of waiting, we are finally able to migrate to new hardware and
Informix 11.5. Yea. This is a chance to make any changes to how the data is
laid out.

I suggesting we start up a second server in read-only mode that reads the same
disk as the primary. Then we can move the ugly sales comparision reports to
the read only server without having to redesign/split the database.

The sales data is very large and is partitioned by division. But there are
some OLTP tables that are partitioned too. Currently the partitions of OLAP
and OLTP tables are spread out over the same set of dbspace.

My question is, does a Shared Disk architecture have any impact on how I
should lay out the partitions? Like should I separte the OLAP and OLTP into
different sets of dbspaces since they will be accesses in different ways by
different servers? Has anyone had any experience with this? Did you find you
wanted to make adjustments?

On the one hand I'm thinking partitioning is partitioning, shared disk should
not make a difference. On the other hand, the system has been so CPU bound,
that fixing the CPU problem may shift the bottleneck to I/O. Anyone have any
experience at how much there disk I/O increased when they releaved a CPU
bottleneck? Since I'm starting at 20 to 30% disk utilization, even doubling it
should only put me in the 40 to 60% range.

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Messages In This Thread

• Shared Disk Server and partitioned tables
  SCOTT ROBERTS -- Saturday, 21 February 2009, at 1:59 p.m.
  • Re: Shared Disk Server and partitioned tables
    Madison Pruet -- Saturday, 21 February 2009, at 9:00 p.m.
  • Re: Shared Disk Server and partitioned tables
    Cesar Inacio Martins -- Sunday, 22 February 2009, at 8:17 a.m.

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