Esm Failover Architecture; Understanding Esm Failover Architecture - IBM TotalStorage DS4000 EXP100 Installation, User's, And Maintenance Manual

ESM failover architecture

Understanding ESM failover architecture

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IBM TotalStorage DS4000 EXP100 Storage Expansion Enclosure: Installation, User's and Maintenance Guide
1220 mm cold
aisle width
Airflow
Figure 8. Example of cold aisle/hot aisle rack configuration
This section provides information about the ESM failover architecture for the
EXP100, including guidelines for creating array configurations that offer maximum
protection of data access in the event of ESM failure.
With full high-availability (FHA) support, the EXP100 R2 or R3 storage expansion
enclosure architecture provides full drive failover and fail-back support for a loss of
connectivity due to failed components in the drive paths (such as failed SFPs, Fibre
Channel cables, ESMs, and so on). In normal operation, each ESM in the EXP100
chassis manages only one-half of the drives in the EXP100 chassis even though
each ESM can access all of the drives as shown in Figure 9 on page 25. The left
ESM manages drives at odd-numbered slots (1, 3, 5, 7, 9, 11, 13); the right ESM
manages drives at even-numbered slots (2, 4, 6, 8, 10, 12, 14).
Note: In contrast to the EXP100 R2 and R3 expansion enclosures, which have
ESM firmware installed that supports full high-availability, EXP100 R1
expansion enclosures have low high-availability (LHA) firmware installed.
Therefore, EXP100 R1 units do not provide SATA hard drive failover or
fail-back support for a loss of connectivity due to bad components in the
Fibre Channel drive paths to the ESM (such as failed SFPs or Fibre Channel
cables). They also do not provide failover or fail-back support for the loss of
an ESM that is in a failed/fault state or that is removed from the EXP100
expansion enclosure chassis. In this case, the controller displays the drive
back
T42 racks
front
Cold aisle
front
T42 racks
back
Hot aisle
back
T42 racks
front
Perforated tiles
or gratings
2440 mm between
center lines of hot
and cold aisle