Appendix A: EonStor U16U Features
Fault Tolerance
A-3
A.4. Fault
Tolerance
A.4.1 Intelligent Drive Handling
Media Scan is an innovative Intelligent Drive Handling function that can be used for data
retrieval from degraded or damaged hard drives. If two bad blocks occur on two member
drives of an array, the integrity of the stored data will be endangered. Intelligent Drive
Handling capabilities can be used to retrieve data from the damaged sectors. Media Scan
is able to handle low quality drives in both the degraded mode and during the rebuild
process. Other Intelligent Drive Handling features, which provide further data security,
include the transparent resetting of hung hard drives, Power-failure management and bad
drive handling during LD expansion.
A.4.2 Auto Switch Cache Policy and Auto Shutdown
When a RAID controller detects conditions that exceed the preset thresholds, the
following actions will be initiated to protect the hardware:
1.
Cached data will be automatically flushed and the array’s caching mode will be
switched from write-back to write-through
2.
If the conditions persist for a preset period of time, auto shutdown of the controller
will commence.
All the thresholds associated with this mechanism are user configurable and, once a
subsystem manager restores the normal operating conditions, the caching mode will
change back from the write-through mode to the write-back mode.
A.4.3 Global and Local Spares
Both Global and Local (dedicated) spares are supported. The controller(s) will
automatically disconnect from a failed drive and start to rebuild data on the spare drive.
The spare drive will then replace the failed drive.
A.4.4 Hot-Swapping of Drives
A failed drive in the EonStor subsystem can be exchanged without turning off the system
or interrupting the smooth operation of the system. Once the failed drive is replaced the
data will be rebuilt in the background. Hot-swapping is supported through the automatic
disconnection from a failed drive and the detection of a reserve drive. All these failure
recovery procedures are completely transparent to the host.
A.4.5 S.M.A.R.T. Support
S.M.A.R.T (Self Monitoring Analysis and Reporting Technology) is supported with
configurable reaction schemes. Users may select different reaction schemes for
immediate prevention against S.M.A.R.T. detected errors. Available options include:
