3.6 Upgrading from OES 1 Linux to OES 2 Linux

Consider the issues in this section when upgrading from OES 1 Linux (with the latest support packs and patches) to OES 2 Linux:

3.6.1 Parameter Settings

When you upgrade the server from OES 1 Linux to OES 2 Linux, all NSS-related parameter settings remain the same as they were before the upgrade. For example, server-level, pool, and volume settings are not modified. All future pools and volumes are created with the default settings for OES 2 Linux.

3.6.2 Read Ahead Blocks Setting

The Read Ahead Blocks parameter specifies the number of data blocks that NSS reads ahead for any open file on which read operations are ongoing in the specified server. Its default setting was changed from 2 blocks in OES 1 Linux to 16 blocks on OES 2 Linux and in a patch on OES 1 SP2 Linux. Volumes created after the patch was installed on OES 1 SP2 Linux have a default setting of 16; however, older volumes might be set to the original default, or to manual settings under 16. After upgrading to OES 2 Linux, if you experience read performance problems with an NSS volume, check the volume’s Read Ahead Blocks parameter setting and change it to at least 16 blocks. A read-ahead value of 2 is too low in most OES 2 Linux environments.

On Linux, you can view or modify the Read Ahead Blocks value by using NSSMU as follows:

  1. In NSSMU, select Volumes to view a list of volumes.

  2. Select the volume, then press Enter to view its Volume Properties list.

  3. Press the arrow keys to go to the Read Ahead Count in Blocks parameter, then press Enter to access the setting.

  4. Type the new count value, then press Enter.

    Valid values are 0 to 1024 blocks, where a block is 4 KB. However, a count of 128 is the practical maximum value. Read-ahead block counts higher than 128 can starve other system components for memory or buffers, which can impair performance or cause the system to hang. As the number of concurrent connections to unique files increase, you should reduce the number of read-ahead blocks.

  5. Press the arrow keys to go to Apply, then press Enter to save and apply the new setting.

You can also modify the value by using the Read Ahead Blocks switches in the NSS Console. For information, see Section A.31, Read Ahead Blocks and Allocate Ahead Blocks Commands.