ibm-information-center/dist/eclipse/plugins/i5OS.ic.rzahq_5.4.0.1/rzahqiscsiattachedperf.htm

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<title>iSCSI attached server performance</title>
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<h3 id="rzahqiscsiattachedperf">iSCSI attached server performance</h3>
<p>For iSCSI attached servers, there are multiple configuration options to
adjust for better performance capacity as needed. Some options may require
different target disk configurations or volumes on the integrated servers.</p>
<p><span class="bold">Windows disk configuration</span></p>
<p>For iSCSI attached integrated servers, the virtual disk drives are optimized
for:</p>
<ul>
<li>1 disk partition per virtual drive.</li>
<li>1 gigabyte or larger storage spaces.</li>
<li>NTFS file system formatted with 4 kilobyte or larger cluster sizes.</li></ul>
<p>These guidelines allow the iSeries&trade; to efficiently manage the storage space
memory, improving the disk performance. These guidelines also affect IXS and
IXA attached servers, but to a much smaller degree.</p>
<p><img src="delta.gif" alt="Start of change" />If you use the Change Network Storage Space (CHGNWSSTG) CL
command to increase a storage space size, be sure to use the Windows Server
2003 DISKPART command to also increase the size of the partition on Windows.
</p>
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<div class="notetitle" id="wq14">Note:</div>
<div class="notebody">For better performance, add a storage space to the server
instead of adding another disk partition in the new space.</div><img src="deltaend.gif" alt="End of change" />
<p><span class="bold">iSeries memory pools</span></p>
<p>For iSCSI attached servers, the storage operations occur through an iSeries memory pool. This memory essentially acts as a cache to the disk operations,
so the size of the memory can affect the Windows disk performance. This I/O
does not directly cause page faulting in the base pool. However, since pool
memory is shared with other i5/OS&trade; applications, Windows disk operations
may cause page faulting in other applications, or other applications may induce
paging of iSCSI disk operations. In extreme cases, you may need to adjust
memory pool sizes or assign applications to other memory pools to mitigate
memory problems.</p>
<p>IXS and IXA attached servers do not perform disk operations through a base
memory pool. They use reserved memory within the machine pool (System Pool
ID 1). Thus, the disk operations do not share memory with other applications.</p>
<p><span class="bold">iSCSI performance configurations</span></p>
<p>On iSCSI attached integrated servers, if a single network fabric is reaching
capacity, you can add channels with additional iSCSI HBAs in both the xSeries&reg; and iSeries servers (assuming the interconnecting network also
has available bandwidth).</p>
<p>There are several ways that you can spread the iSCSI and network traffic
between the separate channels:</p>
<ul>
<li>Dedicate SCSI operations to one channel, and virtual Ethernet operations
to another.</li>
<li>Use two storage targets. Each target should be linked to a separate HBA
paths. See <a href="rzahqmanageiscsihostadapters.htm#rzahqmanageiscsihostadapters">Manage iSCSI host bus adapters</a>.
<ul>
<li>On Windows, direct applications to use both drives (if possible), or dedicate
the drives to different applications to spread the total disk operations between
the drives.</li>
<li>Configure the two disks in a Windows dynamic volume set with the data
striped across the two drives. As applications use the volume, the disk operations
will automatically balance across the drives in the volume set.</li></ul></li></ul><img src="deltaend.gif" alt="End of change" /><img src="deltaend.gif" alt="End of change" />
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