Installation manual

Special LUN considerations
When binding LUNs destined for the reserved LUN pool, give these LUNs high numbers. Place
these LUNs in the “private LUN number” range. If the array to be configured supports a max of
2,048 addressable LUNs, then these reserved LUNs should start at 2100 and increase as more
reserved LUNs are added.
LUN expansion: MetaLUNs
Create metaLUNs from LUNs in separate RAID 5 RAID groups. Use the striping method and wait
for the extra space. This will provide the best performance in the majority of environments.
Striping metaLUNs typically provides high performance but requires the stripe to be built before
the extra space becomes available. Concatenation provides immediate space availability but will
not balance the I/Os across all the drives. The extra space must be used to get the added disk
benefit from the concatenation.
The two can be combined in a concatenated stripe. This provides both immediate space
availability and the potential performance benefit of striping.
For the stripe multiplier use:
• For four-disk LUNs use 4 – a four-disk LUN is a 4+1 RAID 3 or RAID 5 or a 4+4
RAID 1/0.
• For eight-disk LUNs use 2 – an eight-disk LUN is an 8+1 RAID 3 or RAID 5.
• If RAID 1, set to 2.
• A good general purpose number is 4.
LUNs should be expanded onto "like" RAID groups (that is, expand a 4+1 R5 LUN into other 4+1
R5 RAID groups to retain similar geometry).
For user capacity, use the current capacity for planned metaLUN creation. Use the maximum
capacity setting for unplanned metaLUN creation. While metaLUN expansion is supported on all
Dell/EMC CX Series arrays, each operating system has separate restrictions regarding the
support of online capacity expansion. Refer to your operating system vendor for details.
All member LUNs of a metaLUN should be assigned to the same default SP.
Dell/EMC CX Series Initial Configuration
Best Practices Planning 10