Quantum QXS G2 Series, Hardware Installation And Maintenance Manual

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System Overview 7
NOTE: Throughout this guide—and the management interfaces documents used with this
guide—the RAID chassis has two RAID controllers installed and the expansion chassis has two
expansion I/O modules (IOMs) installed.
CompactFlash
During a power loss or controller failure, data stored in cache is saved off to non-volatile memory
(CompactFlash). The data is restored to cache, and 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. The CompactFlash memory card is located at the midplane-facing end of
the controller module. Do not remove the card; it is used for cache recovery only.
NOTE: In dual-controller configurations featuring one healthy partner controller, there is no need to
transport failed controller cache to a replacement controller because the cache is duplicated between
the controllers, provided that volume cache is set to standard on all volumes in the pool owned by
the failed controller.
Supercapacitor Pack
To protect controller module cache in case of power failure, each controller chassis model is equipped
with supercapacitor technology, in conjunction with CompactFlash memory, built into each controller
module to provide extended cache memory backup time.
The supercapacitor pack provides energy for backing up unwritten data in the write cache to the
CompactFlash, in the event of a power failure. Unwritten data in CompactFlash memory is
automatically committed to disk media when power is restored. In the event of power failure, while
cache is maintained by the supercapacitor pack, the Cache Status LED blinks at a rate of 1/10 second
on and 9/10 second off. See also Cache Overview and Status LED Details on page 45.