Dell PowerVault MD3000i Dell PowerVault MD3000/MD3000i Array Tuning Best Pract - Page 22

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices For a complete list of commands and instructions on using the CLI Performance Monitor, refer to the Dell™ PowerVault™ Modular Disk Storage Manager CLI Guide on http://support.dell.com/manuals. 4.9 Other Array Considerations 4.9.1 Global Media Scan Rate Use the Tools tab to change/set the Media Scan settings in the MDSM. Global Media Scan uses CPU cycles and will affect performance if run at an inappropriate time, for example, during high-use user access or during backups. Set up and use Global Media Scan for low access logical drives, for example, file storage drives. Please note that Dell™ does not recommend disabling media scan or lowering the media scan interval below 15 days. If Media-Scan is disabled, the risk of non-predicted failures can increase. 4.9.2 Setting the Virtual Disk-Specific Media Scan Changing/setting the Media Scan settings in the MDSM is on the Tools tab. To choose to run Media Scan on specific virtual disk, highlight the appropriate virtual disk to be scanned, and select the Scan selected virtual disks check box. 4.10 Premium Feature Performance 4.10.1 Getting Optimal Performance from Snapshot When distributing Snapshot Repositories, locate the repository virtual disks on separate drives from production virtual disks to isolate the repository writes and minimize the copy-on-write penalty. When possible, schedule Read I/Os to the Snapshot virtual disk to off-peak times when I/O activity on the source virtual disk is lower such as during evening hours. 4.10.2 Getting Optimal Performance from Virtual Disk Copy The Virtual Disk Copy premium feature uses optimized large blocks to complete the copy as quickly as possible. Thus Virtual Disk Copy requires little tuning other than setting the copy priority to the highest level that still allows acceptable host I/O performance. Virtual Disk Copy performance is affected by other controller activity and by the RAID level and Virtual Disk parameters of the source virtual disk and the target virtual disk. A best practice for using Virtual Disk Copy is to disable all snapshot virtual disks associated with a source virtual disk before selecting the source virtual disk as a virtual disk copy target volume. Target and source virtual disks should ideally be resident on separate disk groups when possible; keeping them on the same disk group raises the potential for lower performing random I/Os for the copy operation. December 2008 - Revision A01 Page 22