70 lines
4.6 KiB
HTML
70 lines
4.6 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="dc.language" scheme="rfc1766" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<meta name="dc.date" scheme="iso8601" content="2005-09-13" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow"/>
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<title>iSeries storage spaces versus dedicated disks</title>
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<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
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<link rel="stylesheet" type="text/css" href="ic.css" />
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</head>
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<img src="delta.gif" alt="Start of change" /><img src="delta.gif" alt="Start of change" />
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<a name="rzahqperfstgvsded"></a>
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<h3 id="rzahqperfstgvsded">iSeries storage spaces versus dedicated disks</h3>
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<p>For performing processor or memory intensive work on an integrated server,
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the performance characteristics are equivalent to a stand-alone server using
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dedicated disk drives. Since the integrated server disk drives are allocated
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out of iSeries™ storage, the disk performance is dependent on the iSeries.</p>
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<p><span class="bold">Greater disk performance capacity with iSeries shared disks</span></p>
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<p>On most stand-alone servers a few disks are dedicated to each server. For
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applications with a small average disk load, the performance is adequate.
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However, there can be periods of time where the server performance is limited
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by the capacity of those few dedicated disks.</p>
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<p>When the same group of servers is integrated with the iSeries, the virtual
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disks are spread across more iSeries hard disks. The total average disk
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load does not need to be any greater than for a group of servers with dedicated
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disks. But, when an individual server temporarily needs more disk performance
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capacity, it is available through the larger set of iSeries disks.</p>
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<p>On servers with dedicated disks, the disk response times tend to be relatively
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steady. For example, you might take advantage of the predictable response
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time and configure the Windows Performance Monitor to produce alerts when
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disk response times exceed typical thresholds and indicate exceptional conditions
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which may need your attention.</p>
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<p>On an integrated server, the iSeries storage, CPU and memory are shared
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between the integrated server and iSeries applications. It is normal for Windows
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disk response to swing through a larger range. Short periods might occur where
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I/O operations from multiple integrated servers, or other iSeries operations
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contend for the same disk. Some disk intensive iSeries applications (like SAV and RST), can
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reduce the disk performance seen on the Windows server for a period of time.
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This can make it more difficult to choose a threshold value for short time
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periods.</p>
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<p><span class="bold">Consider the entire group of disks when you evaluate storage
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bottlenecks</span></p>
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<p>The iSeries server storage space appears as one disk drive within Windows.
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When the Physical Disk average queue length (in Windows Performance Monitor)
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exceeds two, the server performance is not necessarily disk constrained. Assuming
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that memory paging issues have been ruled out, a queue length of two or a
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Windows disk utilization of 100% only points to a storage bottleneck if there
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is only one physical disk drive to perform the operations. There are usually
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multiple disks on the iSeries server in the storage space ASP operating in parallel.
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Typically, two times the number of disks in the ASP might point toward a disk
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bottleneck. You might also need to account for the average queue lengths of
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all the servers using the storage ASP.</p><img src="deltaend.gif" alt="End of change" /><img src="deltaend.gif" alt="End of change" />
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<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
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</body>
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</html>
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