138 lines
8.0 KiB
HTML
138 lines
8.0 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="topic" />
|
|
<meta name="DC.Title" content="Comparison of disk protection options" />
|
|
<meta name="DC.Relation" scheme="URI" content="rzalyprtctvsdtalss.htm" />
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 2002, 2006" />
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2002, 2006" />
|
|
<meta name="DC.Format" content="XHTML" />
|
|
<meta name="DC.Identifier" content="hdrcmpropts" />
|
|
<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>Comparison of disk protection options</title>
|
|
</head>
|
|
<body id="hdrcmpropts"><a name="hdrcmpropts"><!-- --></a>
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
|
<h1 class="topictitle1">Comparison of disk protection options</h1>
|
|
<div><p>You should be aware of these considerations when selecting disk protection
|
|
options:</p>
|
|
<p>When using RAID 5 device parity protection, the system continues
|
|
to run after a single-disk failure. When using RAID 6 device parity protection,
|
|
the system continues to run after a two-disk failure. With mirrored protection,
|
|
the system might continue to run after the failure of a disk-related component,
|
|
such as an IOA or an IOP. </p>
|
|
<p>RAID 5 device parity protection requires the capacity of one
|
|
disk unit that is dedicated to storing parity data in a parity set. RAID 6
|
|
device parity protection requires the capacity of two disk units that are
|
|
dedicated to storing parity data in a parity set. A system with mirrored protection
|
|
requires twice as much disk capacity as the same system without mirrored protection
|
|
because all information is stored twice. Mirrored protection might also require
|
|
more buses, IOPs, and disk IOA, depending on the level of protection that
|
|
you want. Therefore, mirrored protection is typically more expensive than
|
|
device parity protection. </p>
|
|
<p>Typically, neither device parity protection nor mirrored protection has
|
|
a noticeable effect on system performance. In some cases, mirrored protection
|
|
actually improves system performance. The time required to restore data to
|
|
disk units that are protected by device parity protection is longer than the
|
|
time required to restore to the same disk devices that do not have device
|
|
parity protection activated. This is because the parity data must be calculated
|
|
and written.</p>
|
|
<div class="p">This table provides an overview of the availability tools that can be used
|
|
on the server to protect against different types of failure.
|
|
<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr class="tablemainheaderbar"><th class="oddrowblue" align="left" valign="bottom" width="48%" id="d0e29">What type of
|
|
availability is needed?</th>
|
|
<th class="oddrowblue" align="left" valign="bottom" width="13%" id="d0e31">Device parity
|
|
protection</th>
|
|
<th class="oddrowblue" align="left" valign="bottom" width="13%" id="d0e33">Mirrored protection</th>
|
|
<th class="oddrowblue" align="left" valign="bottom" width="13%" id="d0e35">Basic disk pools</th>
|
|
<th class="oddrowblue" align="left" valign="bottom" width="13%" id="d0e37">Independent disk
|
|
pool</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody><tr><td align="left" valign="top" width="48%" headers="d0e29 ">Protect from data loss due to disk-related
|
|
hardware failure</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">See note 2</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">See note 2</td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Maintain availability</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">Yes<sup>4</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Help with disk unit recovery</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">Yes<sup>2</sup></td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">Yes<sup>2</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Maintain availability when input/output adapter
|
|
(IOA) fails</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes<sup>1</sup></td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">No<sup>5</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Maintain availability when disk I/O processor
|
|
fails</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes<sup>1</sup></td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">No<sup>5</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Maintain availability when system bus fails</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes<sup>1</sup></td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">No<sup>5</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Site disaster protection</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">Yes<sup>3</sup></td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">No<sup>5</sup></td>
|
|
</tr>
|
|
<tr><td align="left" valign="top" width="48%" headers="d0e29 ">Ability to switch data between systems</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e31 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e33 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e35 ">No</td>
|
|
<td align="left" valign="top" width="13%" headers="d0e37 ">Yes</td>
|
|
</tr>
|
|
<tr><td colspan="5" align="left" valign="top" headers="d0e29 d0e31 d0e33 d0e35 d0e37 "> <p><span class="uicontrol">Notes:</span></p>
|
|
<ol><li>Depends on hardware used, configuration, and level of mirrored protection.</li>
|
|
<li>Configuring disk pools can limit the loss of data and the recovery to
|
|
a single disk pool.</li>
|
|
<li>For site disaster protection, remote mirroring is required.</li>
|
|
<li>In a clustered environment, an independent disk pool can help maintain
|
|
availability.</li>
|
|
<li>When using geographic mirroring, independent disk pools can provide site
|
|
disaster protection.</li>
|
|
</ol>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalyprtctvsdtalss.htm">Plan for disk protection</a></div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html> |