Dell 651F, 650F User Manual 2
CHAPTER 17
SAN Performance Tuning
This chapter provides information and instructions for improving the performance of
the various storage area network (SAN) components in your network. All procedures
in this document require administrator access permissions.
This chapter provides information about the following components:
• Dell OpenManage Data Managed Node Data Agent for 650F and 651F storage
systems
• Running multiple copies of Data Managed Node Data Agent in a SAN
• RAID considerations for 650F and 651F storage systems
• Cache size for 650F and 651F storage systems
• Setting the execution throttle
• Setting the PowerVault 650F and 651F cache water mark
• Network timeouts
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Dell OpenManage Data Managed Node Data Agent for 650F and 651F Storage Systems
When the Dell OpenManage Application Transparent Failover (ATF) software is not
installed, the Dell OpenManage Data Managed Node Data Agent’s commands for
polling and configuring the 650F and 651F storage systems are intermixed with the
normal input/output (I/O) activities that are being generated by the system application
programs. This intermixing of the different types of I/O causes the management I/O
to be delayed, which causes the Dell PowerVault manager applications to time out
while communicating with the array. If a system is experiencing I/O time-out errors
during heavy I/O activity, you can improve performance by changing the agent management I/O path to go through a dedicated logical unit number (LUN) rather than the
physical drive device driver. Change the entries in the Data Agent Configurator’s
Device window to specify the dedicated LUN by performing the following steps:
1. Click Start—> Programs—> Dell OpenManage PowerVault Manager—>
Data Managed Node—> Data Agent.
SAN Performance Tuning 17-1
2. In the Data Agent Configurator window, click the Devices menu and then click
Auto-Detec t to force the disk array to be discovered.
3. Modify the Device entries to point to the same LUN. For example, if the Device
window contains the following lines:
\\.\SCSI2:0:0:0:0
\\.\SCSI3:0:0:1:1
Modify the lines as follows:
\\.\SCSI2:0:0:0:7
\\.\SCSI3:0:0:1:7
ThelastfieldinthedevicestringrepresentstheLUN,whichisLUN7inthis
example. After a specific LUN is dedicated to the agent’s communication path, do
not create another LUN with the same LUN ID.
Running Multiple Copies of Data Managed Node Data Agent in a SAN
SAN performance can be affected by the number of copies of Dell OpenManage Data
Managed Node Data Agent that are running in a SAN. You should run one copy (or two
for backup) in your SAN. If you run Data Managed Node Data Agent on all of the
servers in the SAN that have PowerVault 650F, 651F, and 630F storage systems
allocated to them, you will experience a significant performance degradation on your
storage systems.
RAID Considerations for 650F and 651F Storage Systems
Although you are allowed to bind RAID 5 LUNs containing from three to sixteen harddisk drives, performance for this type of RAID has been optimized for from five to
nine hard-disk drives. Under some circumstances, more than nine hard-disk drives
can degrade performance. To improve performance, you can reconfigure the number
of hard-disk drives you bind to each LUN.
17-2 Dell PowerVau lt SAN Admini stra tor’sGuide
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