95 lines
6.2 KiB
HTML
95 lines
6.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE html
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html lang="en-us" xml:lang="en-us">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="security" content="public" />
|
|
<meta name="Robots" content="index,follow" />
|
|
<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))' />
|
|
<meta name="DC.Type" content="concept" />
|
|
<meta name="DC.Title" content="Extended Adaptive Cache Concepts" />
|
|
<meta name="abstract" content="Explore Extended Adaptive Cache. Find information about planning, restrictions, and important considerations before you begin to use this tool." />
|
|
<meta name="description" content="Explore Extended Adaptive Cache. Find information about planning, restrictions, and important considerations before you begin to use this tool." />
|
|
<meta name="DC.Relation" scheme="URI" content="rzahxintro.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="rzahxeacplan.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="rzahxeacuse.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="../rzalm/rzalmlvm.htm" />
|
|
<meta name="DC.Relation" scheme="URI" content="../rzaly/rzalymirrorconcept.htm" />
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Format" content="XHTML" />
|
|
<meta name="DC.Identifier" content="rzahxeac1" />
|
|
<meta name="DC.Language" content="en-us" />
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
|
<!-- US Government Users Restricted Rights -->
|
|
<!-- Use, duplication or disclosure restricted by -->
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
|
<title>Extended Adaptive Cache Concepts</title>
|
|
</head>
|
|
<body id="rzahxeac1"><a name="rzahxeac1"><!-- --></a>
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
|
<h1 class="topictitle1">Extended Adaptive Cache Concepts</h1>
|
|
<div><p>Explore Extended Adaptive Cache. Find information about planning,
|
|
restrictions, and important considerations before you begin to use this tool.</p>
|
|
<p>Improve system performance with Extended Adaptive Cache, an advanced read
|
|
cache technology that improves both the I/O subsystem and system response
|
|
times by reducing the number of physical I/O requests that are read from disk.
|
|
Extended Adaptive Cache not only improves the performance of database-read
|
|
actions, but of all read actions. This includes read actions that are generated
|
|
by other system components such as the <span class="keyword">Integrated xSeries<sup>®</sup> Server</span>.
|
|
It also works effectively in storage subsystems that have device parity protection
|
|
or mirrored protection. Extended Adaptive Cache has proven to be highly effective
|
|
on many types of workloads.</p>
|
|
<div class="section"><h4 class="sectiontitle">How the Extended Adaptive Cache works</h4><p>Extended Adaptive
|
|
Cache is integrated into the <span class="keyword">iSeries™</span> I/O
|
|
subsystem. It operates at the disk subsystem controller level and does not
|
|
affect the <span class="keyword">iSeries</span> system processor.
|
|
The storage I/O adapter manages the Extended Adaptive Cache by using a Read
|
|
Cache Device (such as a solid state disk) to provide the cache memory.</p>
|
|
<p>Extended
|
|
Adaptive Cache generates statistical information for the data, and then uses
|
|
a mix of management strategies to determine which data to cache. The management
|
|
of the cache is performed automatically within the I/O adapter and is designed
|
|
to cache data by using a predictive algorithm. The algorithm considers how
|
|
recently and how frequently the host has accessed a predetermined range of
|
|
data.</p>
|
|
<p>The design of Extended Adaptive Cache was based on specific data
|
|
management strategies of the <span class="keyword">iSeries</span> server.
|
|
Whether the disks are device parity protected, mirrored, or unprotected, the
|
|
data stored on the disks has a tendency to occur in bands. This means that
|
|
there are physically contiguous areas of disk storage where data is actively
|
|
read, physically contiguous areas that are frequently written to, physically
|
|
contiguous areas that are both actively read and written to, or physically
|
|
contiguous areas of storage that are not frequently accessed.</p>
|
|
<p>This "banding"
|
|
of data is accounted for in the Extended Adaptive Cache design. The goal is
|
|
to cache bands characterized as read/write and read-only. A band that is characterized
|
|
as write-only, while cached in the storage subsystem write cache, remains
|
|
largely unaffected by Extended Adaptive Cache. Extended Adaptive Cache is
|
|
also designed to not harm the performance of large blocks of data that are
|
|
either sequentially written or sequentially read. In this instance, the pre-fetch
|
|
capability of the disks, as well as other caches in the system, ensures a
|
|
quick response time.</p>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<ul class="ullinks">
|
|
<li class="ulchildlink"><strong><a href="rzahxeacplan.htm">Restrictions and considerations for Extended Adaptive Cache</a></strong><br />
|
|
See what components Extended Adaptive Cache requires and learn more about what to expect.</li>
|
|
<li class="ulchildlink"><strong><a href="rzahxeacuse.htm">Start Extended Adaptive Cache</a></strong><br />
|
|
To start Extended Adaptive Cache and increase your system's performance, purchase the Read Cache Device.</li>
|
|
</ul>
|
|
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahxintro.htm" title="You can use Extended Adaptive Cache to improve system performance by collecting disk usage data, and then using those statistics to create a cache, effectively reducing the physical I/O requests for the disk.">Extended Adaptive Cache</a></div>
|
|
</div>
|
|
<div class="relconcepts"><strong>Related concepts</strong><br />
|
|
<div><a href="../rzalm/rzalmlvm.htm">Device parity protection</a></div>
|
|
<div><a href="../rzaly/rzalymirrorconcept.htm">Mirrored protection</a></div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html> |