Exporting luns to initiators – Dell Acceleration Appliances for Databases User Manual
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• Use the 512B sector size when exporting volumes to initiators. If you need to export LUNs
with a 4KB sector size, use Oracle or third-party-provided ASMLIB support packages. ASMLIB
support is now available for RHEL 6.x. For details, visit this link:
You may also need to use the
_disk_sector_size_override
parameter to overcome an
Oracle ASM diskgroup creation error.
• ASM distributes data on all the ASM disks in the disk group. A diskgroup can be created
with an option for NORMAL REDUNDANCY (two-way mirroring), HIGH REDUNDANCY
(three-way mirroring) or EXTERNAL REDUNDANCY (no mirroring). For ION Accelerator, no
significant performance differences have been observed between these ASM mirroring
options.
• It is generally advisable to use the default 1MB allocation unit (AU) size. For larger (3TB+)
databases, the AU size can be increased to 4M or 8M.
• If more than 2 IONs used (without HA options), then by carefully creating ASM diskgroup
mirroring options can avoid outages due to the rare scenario of ION node/component
failures. For example, if you have 3 set of ION volumes from 3 different ION nodes and all
part of a HIGH redundancy mirroring option, then losing 2 IONs completely would still make
the application function without an issue (assuming the free space is enough for the
database transactions).
EXPORTING LUNS TO INITIATORS
In RAC, it’s recommended to have separate, small ION Accelerator volumes for Oracle cluster voting
disks, with Normal or High redundancy ASM mirroring. Optionally, versions 11gR2 and 12c support
voting disks as part of regular ASM diskgroups. Careful planning is needed here to avoid Oracle RAC
node evictions.
For Oracle RAC configuration, it’s recommended to have one initiator group for all participating
Oracle initiator nodes. This will greatly decrease the time spent in LUN-mapping.
If you are planning to assign LUNs to various initiators, you should create the initiator groups
individually.
Because LUN mappings include the target/initiator port addresses, it’s strongly recommended to tag
the cables and ports. This will help in reconnecting to the same ports if the direct-connected cables
needed to be removed or exchanged.
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