Advanced Backup to Disk Performance White Paper

Tuning Recommendations
General
• Ensure the Ultra320 SCSI HBA for the tape drive is placed on a dedicated 133-MHz PCI-X bus and
is not sharing the bus with other HBAs.
• For all HP StorageWorks Ultrium 960 backups, HP recommends the Tape Block Size be configured
to 256 KB.
• Match file library block size to tape drive block size. When using a secondary subsystem as a file
library for backups, it is important to give it the same block size as the tape device that will be used
in the final part of the data protection process. So in the case of HP StorageWorks Ultrium 960
tape drive, this would be 256 KB. Different block size between source and target medium will
cause block repackaging which has an performance impact in regards to additional CPU load,
CRC processing (if enabled) and shared memory utilization.
• Disable double tree walks for file systems with millions of small files. The first tree walk briefly scans
the files selected for the backup and calculates its size, so that the percentage done can be
calculated during the backup. The second tree walk is executed during the actual file backup. On
these particular systems, it is recommended to set the option “NoTreeWalk=1” in the Data Protector
configuration file “<Data_Protector_home>\omnirc”.
• In Windows environments, configure smaller file depot sizes for better performance. Creating larger
files requires more CPU and memory resources. For similar environments the recommended
Maximum File Depot Size is 10 – 50 GB.
• Windows memory problems can occur during high performance backups. This is a general
Windows kernel problem and applies to all backup applications – including NTBACKUP.
The Data Protector error message looks like:
[Major] From: [e-mail] "G:" Time: 29.03.2005 19:08:57
[81:78] G:\1\file67108864_000003
Cannot read 57256 bytes at offset 0(:1): ([1450] Insufficient system resources
exist to complete the requested service. ).
A Microsoft article (Q304101) has been found that explains the circumstances that can lead to this
error and how to fix it.
Note: It's suggested to follow the instructions in Microsoft article Q304101, where causes and
settings for avoiding memory problems are described. The link to this article:
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q304101
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