IBM TotalStorage EXP100, Инструкция по установке, использованию и обслуживанию

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To protect against multiple failures like failures in both ESMs, failures in the Fibre
Channel connections to both ESMs in the EXP100 chassis, or a failure in the whole
EXP100 chassis, you should follow the guidelines outlined in the next section.
Configuration guidelines
v
To protect against hard drive failure, reserve at least one drive in each EXP100
enclosure as a global hot-spare drive.
v The best way to protect against the loss of data availability due to ESM or
EXP100 failure is to orthogonally stripe the array over multiple expansion
enclosures. The disadvantage of this method lies in the number of EXP100
expansion enclosures that you need for this type of striping.
To orthogonally stripe the array over multiple expansion enclosures, you must
have one EXP100 expansion enclosure available for every drive that is to be
defined in a RAID array. This means you would need two EXP100 expansion
enclosures to create a two-drive RAID-1. For a five-drive RAID-5 array, you
would need five EXP100 expansion enclosures (and so on, up to the maximum
number of EXP100s that are supported with a particular storage subsystem –
eight expansion enclosures for the DS4300 and 16 expansion enclosures for the
DS4500).
Figure 12 on page 28 and Figure 13 on page 28 show examples of arrays that
are orthogonally striped over multiple EXP100 expansion enclosures. If an ESM
in a EXP100 failed, or even if the entire EXP100 expansion enclosure failed, the
defined arrays would enter a Degraded (but not Failed) state. Consequently, no
direct data availability impact would occur in this situation, and ESM replacement
could be used to restore the system to a fully optimal state without any loss of
access to data.
1 2 3 4 5 6 7 8 9 10 11 12 13 14
left ESM
FC OUT FC IN
From
controller
drive port or
FC port in
another
EXP100
From
controller
drive port or
FC port in
another
EXP100
To controller
drive port or
FC port in
another
EXP100
To controller
drive port or
FC port in
another
EXP100
Port Bypass Logic
FibreChannel-SATA
Bridge
FC OUT FC IN
FibreChannel-SATA
Bridge
right ESM
Internal ESM --
ESM link
Port Bypass Logic
exp12cfg9
Figure 11. Right ESM reroutes I/Os along dashed alternate paths
Chapter 1. Introduction
27
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