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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Understanding RAID level-0</title>
<base target="_top">
<link rel="stylesheet" href="basicpg.css">
</head>
<body text="#000000" bgcolor="#FFFFFF" link="#0000FF" vlink="#333399" alink="#0000FF">
<h1>Understanding RAID level-0 </h1>
<p>RAID level-0 <a href="gs-unit.htm">stripes</a> the data across all the drives
in the disk group. This offers substantial speed enhancement, but provides no data
redundancy. RAID level-0 provides the largest storage capacity of the RAID levels
that are offered, because no room is taken for redundant data or data-<a href="gparity.htm">parity</a>
storage. </p>
<p> RAID level-0 requires a minimum of two drives and, depending upon the level
of firmware and the <a href="cstripe.htm">stripe size</a>, supports a maximum
of 48 drives.
<p> The following illustration shows an example of a RAID level-0 logical device.
<h2>RAID level-0 example</h2>
<table border="0" cellpadding="3">
<tr valign=top>
<td align="LEFT" valign="TOP" width="258">Start with two physical drives.
</td>
<td width="133"><img src="images/raidl0-a.gif" width="107" height="93" alt="RAID Level 0 example">
</td>
</tr>
<tr valign=top>
<td align="LEFT" valign="TOP" width="258">Create a disk group using the two physical
drives. </td>
<td width="133"><img src="images/raidl0-b.gif" width="107" height="93" alt="RAID Level 0 example">
</td>
</tr>
<tr valign=top>
<td align="LEFT" valign="TOP" width="258">Then create a logical device within
that disk group. </td>
<td width="133"><img src="images/raidl0-c.gif" width="107" height="93" alt="RAID Level 0 example">
</td>
</tr>
<tr valign=top>
<td align="LEFT" valign="TOP" width="258">The data is striped across the drives,
creating blocks.
<p>Notice that the data is striped across all the drives in the disk group, but
no redundant data is stored.
</td>
<td width="133"><img src="images/raidl0-d.gif" width="107" height="93" alt="RAID Level 0 example">
</td>
</tr>
</table>
<p>A physical drive failure within the disk group results in loss of data in the logical
drive assigned RAID level-0, but only in that logical device. If you have logical
drives assigned <a href="craid1.htm">RAID level-1</a> or
<a href="craid5.htm">5</a> in the same disk group,
they will not lose data. </p>
<p>When you replace a failed drive, the controller can rebuild all the
RAID level-1 and 5 logical devices automatically onto the replacement
physical drive. However, any data stored in a failed RAID level-0 logical device
is lost.
<p>Although the risk of data loss is present, you might want to assign RAID level-0
to one of the logical devices to take advantage of the speed this RAID level
offers. You can use this logical device to store data that you back up each day
and can re-create easily. You also might want to use a RAID level-0 logical
drive when you require maximum capacity.
<p>RAID level-0 offers the following advantages and disadvantages. <br>
<table BORDER>
<tr bgcolor="#C0C0C0">
<th align="LEFT" valign="BOTTOM" width="50%">Advantages </th>
<th align="LEFT" valign="BOTTOM" width="50%">Disadvantages </th>
</tr>
<tr>
<td align="LEFT" valign="TOP" width="50%">
<ul>
<li>Substantial speed enhancement </li>
<li>Maximum utilization of physical drive storage capacity, because no
room is taken for redundant data or data-parity storage </li>
</ul>
</td>
<td align="LEFT" valign="TOP" width="50%">No data redundancy, resulting in
data loss in the event that a physical drive fails </td>
</tr>
</table>
<h2>More information</h2>
<ul>
<li><a href="craidint.htm">Understanding RAID technology</a></li>
<li><a href="cstripe.htm">Understanding stripe size</a></li>
<li><a href="cselraid.htm">Selecting a RAID level</a> </li>
<li><a href="craid1.htm">RAID level-1</a></li>
<li><a href="craid5.htm">RAID level-5</a></li>
<li><a href="craidx0.htm">RAID level-x0</a> </li>
<li><a href="craidvol.htm">RAID volumes</a></li>
</ul>
<div align="center">
<hr>
<a href="gportal.htm">Glossary</a> | <a href="menutoc.htm">Contents</a></div>
<p> </p>
<p align="right">x-1045-ASM-00-04-EN </p>
</body>
</html>