14 Components
Drive enclosures
Drive enclosure expansion modules attach to MSA 2050 controller modules via the mini-SAS expansion port, allowing addition
of disk drives to the system. MSA 2050 controller enclosures support adding the 6 Gb drive enclosures described below.
LFF and SFF drive enclosure — rear panel layout
MSA 2050 controllers support the MSA 2050 LFF Disk Enclosure and the MSA 2050 SFF Disk Enclosure, which share the
same rear panel layout, as shown below.
Figure 7 Supported drive enclosures: SFF/LFF rear panel
Cache
To enable faster data access from disk storage, the following types of caching are performed:
• Write-back or write-through caching. The controller writes user data in the cache memory on the module rather than
directly to the drives. Later, when the storage system is either idle or aging—and continuing to receive new I/O
data—the controller writes the data to the drive array.
• Read-ahead caching. The controller detects sequential array access, reads ahead into the next sequence of data, and
stores the data in the read-ahead cache. Then, if the next read access is for cached data, the controller immediately
loads the data into the system memory, avoiding the latency of a disk access.
NOTE: See the SMU Reference Guide for more information about volume cache options.
Transportable CompactFlash
During a power loss or array controller failure, data stored in cache is saved off to non-volatile memory (CompactFlash).
The data is then written to disk after the issue is corrected. To protect against writing incomplete data to disk, the image
stored on the CompactFlash is verified before committing to disk.
1 Power supplies (AC shown)
2 I/O module A
3 I/O module B
4 Disabled button (used by engineering only)
5 Service port (used by service personnel only)
6 SAS In port
7 SAS Out port
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