Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 30

members in the pool. The system automatically rebalances the load as the group scales. These operations are transparent to the servers, applications, and users. Group: Configuration Recommendations Before you configure a group, review the following recommendations. • Make sure all the network interfaces on the members are configured, functioning, and accessible. If you have any issues, contact Dell Technical Support. NOTE: Limit configuration changes when a group has members that are offline. If you have members offline or a partitioned network, do not make configuration changes before you correct the problem to bring the group back to normal operation. • Make sure the group has enough storage capacity. Low storage pool capacity generates an alert in SAN Headquarters. If a pool has less than 5 percent free space (or less than 100GB per member, whichever is less), a PS Series group might not have sufficient free space to efficiently perform the virtualization functions required for automatic optimization of the SAN. In addition, when storage pool free space is low, write performance on thin-provisioned volumes is automatically reduced to slow the consumption of free space. If pool capacity is low, try one or more of the following remedies: - Move volumes from the low-space pool to a different pool. - Increase pool member capacity by fully populating the drive bays or upgrading to higher-capacity disks. - Increase pool capacity by adding a member. - Reduce the amount of in-use storage space by deleting unused volumes or by reducing the amount of snapshot reserve. • RAID policy Consider changing the RAID policy for a member. Change the policy only if you are sure that your applications will perform better with a different RAID level. For example, RAID 10 performs better than other RAID levels when a disk drive fails and when a RAID set is degraded. In addition, RAID policies with spare disks provide additional protection against drive failures. NOTE: You can change a RAID policy for a member only if the new RAID policy does not reduce the amount of available disk space. See Supported RAID Policy Conversions for more information. • Volume management - Applications - Assign application volumes to a pool that includes members with the RAID policy that is optimal for the application. - Automatic load balancing - User fewer pools and let the group perform automatic performance load balancing. • Hardware and firmware - To configure a hybrid array (model XS or XVS) to use RAID6 accelerated, the array must contain seven or more valid SSD drives at the time that the array is first set up. - Make sure member control module caches are in write-back mode. - Make sure all the group members are running the latest PS Series firmware. • iSCSI connections Large, complex environments can use many iSCSI connections. A storage pool in a PS Series group can support numerous simultaneous connections, as described in the release notes for the particular Dell EqualLogic firmware release. These connections can be used for fully provisioned volumes, thin-provisioned volumes, snapshots, and control volumes (examples of control volumes are protocol endpoints and VDS/VSS). Attempting to exceed the supported number of connections results in an error message. You can reduce the number of iSCSI connections to the volumes and snapshots in a storage pool in several ways: - Disconnect from unused volumes and snapshots. - Modify MPIO settings to reduce the number of connections per volume. - Move volumes to another storage pool. - Create a new storage pool and move volumes to the new storage pool. • Multipath I/O MPIO provides additional performance capabilities and network path failover between servers and volumes. For certain operating systems, the connections can be automatically managed. If MPIO is not creating multiple connections, you should: 30 Architecture Fundamentals