Best Practices for Mirroring
Before you create mirrors, plan out the high availability strategy.
IMPORTANT: Mirror path configurations, such as using specific mirror paths or redundant mirror paths, must be configured prior to creating a mirror. After a mirror configuration exists for a virtual volume, mirror path settings cannot be changed. Refer to Specifying the Mirror Path.
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Standard mirrors protect against storage failure, not path (switch, storage server) failure. For full path protection, use AP, MPIO, or a Third Party HA option.
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Only mirror volumes that contain data that needs to be highly available. Do not mirror data that is temporary or non-essential.
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Each virtual volume (or mirror) name created in the SAN must be unique. In addition, do not use the same virtual volume name on storage servers on different SANs if the possibility exists that the storage servers could map virtual volumes to the same application server. This could cause the application server to operate under the assumption that the same storage volume is configured over multiple paths.
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Use dedicated mirror paths.
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For efficient use of disk space, both mirror volumes should be the same size.
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Balance the mirroring load. For example, if you need 100 mirrored volumes, consider defining 50 on Storage Server 1 with mirrors to Storage Server 2, and 50 on Storage Server 2 with mirrors to Storage Server 1. Refer to Specifying the Mirror Path.
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Synchronous mirroring typically takes place over dedicated high-throughput routes with separations up to 100 kilometers. For longer distances, use asynchronous mirroring such as AIM. Asynchronous mirrors cannot be used for instant failover in the event of a problem at the source.