50 Planning: MD3600f Series Storage Array Terms and ConceptsDisk Group OperationsRAID Level MigrationYou can migrate from one RAID level to another depending on yourrequirements. For example, fault-tolerant characteristics can be added to astripe set (RAID 0) by converting it to a RAID 5 set. MDSM providesinformation about RAID attributes to assist you in selecting the appropriateRAID level. You can perform a RAID level migration while the system is stillrunning and without rebooting, which maintains data availability.Segment Size MigrationSegment size refers to the amount of data (in KB) that the storage array writes ona single physical disk in a virtual disk before writing data on the next physical disk.Valid values for the segment size are 8 KB, 16 KB, 32 KB, 64 KB, 128 KB, 256KB, and 512 KB.Dynamic segment size migration enables the segment size of a given virtual diskto be changed. A default segment size is set when the virtual disk is created, basedon such factors as the RAID level and expected usage. You can change the defaultvalue (128 KB) if segment size usage does not match your needs.When considering a segment-size change, two scenarios illustrate differentapproaches to the limitations:• If I/O activity stretches beyond the segment size, you can increase it toreduce the number of disks required for a single I/O. Using a single physicaldisk for a single request frees disks to service other requests, especiallywhen you have multiple users accessing a database or storage environment.• If you use the virtual disk in a single-user, large I/O environment (such asfor multimedia application storage), performance can be optimized whena single I/O request is serviced with a single data stripe (the segment sizemultiplied by the number of physical disks in the disk group used for datastorage). In this case, multiple disks are used for the same request, buteach disk is only accessed once.
