Administrator Guide

NOTE: If you need more network bandwidth for iSCSI I/O, do not congure a dedicated management network.
Storage Pool Capacity
Low storage pool capacity is a problem that generates an alert in SAN Headquarters. If a pool has less than 5 percent of free space
(or less than 100GB per member, whichever is less), a PS Series group might not have sucient free space to eciently 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 dierent pool.
• Reduce the amount of in-use storage space by deleting unused volumes or by reducing the amount of snapshot reserve.
• Increase pool member capacity by fully populating the drive bays or upgrading to higher-capacity disks.
• Increase pool capacity by adding a member.
• Move delegated space to a dierent pool.
RAID Policy
Consider changing the RAID policy for a member. Change the policy only if you are sure your applications will perform better with a
dierent RAID level. 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 uses less disk space than the current
RAID policy.
Volume Management
• Assign application volumes to a pool that includes members with the RAID policy that is optimal for the application.
• Automatic load balancing — Consider not binding volumes to a particular group member or using fewer pools, and let the group
perform automatic performance load balancing.
Hardware and Firmware
• Replace member disk drives with higher-performing drives. Make sure the array is fully populated with disk drives.
• Make sure member control module caches are in write-back mode.
• Make sure all the group members are running the latest PS Series rmware.
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 Dell EqualLogic PS Series Storage Arrays Release Notes. These connections can be
used for fully provisioned volumes, thin-provisioned volumes, and snapshots.
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 Windows Server
systems, the connections can be automatically managed. If MPIO is not creating multiple connections, you should:
• Verify that the storage pool does not have the maximum number of iSCSI connections for the release in use. See the Dell
EqualLogic PS Series Storage Arrays Release Notes.
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