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3-16
EMC Fibre Channel Storage-System Configuration Planning
Planning File Systems and LUNs with Shared Switched Storage
per RAID Group may adversely impact performance. If you want
multiple LUNs per RAID Group, then use a RAID Group/LUN
series of entries for each LUN.
Disk IDs. Enter the ID(s) of all disks that will make up the LUN
or hot spare. These are the same disk IDs you specified on the
previous worksheet. For example, for a RAID 5 Group in the DPE
(enclosure 0, disks 2 through 6), enter 0_2, 0_3, 0_4, 0_5, and 0_6.
SP. Specify the SP that will own the LUN: SP A or SP B. You can
let the management program automatically select the SP to
balance the workload between SPs; to do so, leave this entry
blank.
RAID type. Copy the RAID type from the previous worksheet.
For example, RAID 5 or hot spare. For a hot spare (not strictly
speaking a LUN at all), skip the rest of this LUN entry and
continue to the next LUN entry (if any).
If this is a RAID 3 Group, specify the amount of SP memory for
that group. To work efficiently, each RAID 3 Group needs at least
6 Mbytes of memory.
Caching. If you want to use caching (entry on page 3-14), you can
specify whether you want caching — read and write, read, or
write for this LUN. Generally, write caching improves
performance far more than read caching. The ability to specify
caching on a LUN basis provides additional flexibility, since you
can use caching for only the units that will benefit from it. Read
and write caching recommendations follow.
Table 3-1 Cache Recommendations for Different RAID Types
Servers that can access this LUN. Enter the name of each server
(copied from the LUN and Storage Group worksheet).
Operating system information: Device name. Enter the
operating system device name, if this is important and if you
know it. Depending on your operating system, you may not be
able to complete this field now.
RAID 5 RAID 3 RAID 1 RAID 1/0 RAID 0 Individual Unit
Highly Recommended Not allowed Recommended Recommended Recommended Recommended