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EMC Fibre Channel Storage System Model FC4700 Configuration Planning Guide
Planning File Systems and LUNs
Competing the LUN Details Worksheet
Complete the header portion of the worksheet for each storage
system as described next. Copy the blank worksheet as needed.
Storage-System Entries
Storage-system installation type: specify Unshared Direct,
Shared-or-Clustered Direct, or Shared Switched.
SP information: IP address or hostname. The IP address is
required for communication with the SP. You don’t need to
complete it now, but you will need it when the storage system is
installed so that you can set up communication with the SP.
Port ALPA ID. This must be unique for each SP in a storage
system. The SP Port ALPA ID, like the IP address, is generally set
at installation. One easy way to do this is to set SP Port 0 to ALPA
ID 0 and SP 1 Port 1 to ALPA Port 1.
Memory (Mbytes). Each SP can have 256 or 512 Mbytes of
memory.
Caching. You can use SP memory for read/write caching or
RAID 3. (Using both caching and RAID 3 in the same storage
system is not recommended.) You can use different cache settings
for different times of day. For example, for user I/O during the
day, use more write cache; for sequential batch jobs at night, use
more read cache. You enable caching for specific LUNs —
allowing you to tailor your cache resources according to priority.
If you choose caching, check the box and continue to the next
cache item; for RAID 3, skip to the LUN ID entries.
Read cache size. If you want a read cache, it should generally be
about one third of the total available cache memory.
Write cache size. The write cache should be two thirds of the total
available. Some memory is required for system overhead, so you
cannot determine a precise figure at this time. For example, for
256 Mbytes of total memory, you might have 240 Mbytes
available, and you would specify 80 Mbytes for the read cache
and 160 Mbytes for the write cache.
Cache page size. This applies to both read and write caches. It can
be 2, 4, 8, or 16 Kbytes.
As a general guideline, we suggest 8 Kbytes. The ideal cache page
size depends on the operating system and application.