Monitoring IO Accelerator health
NAND flash and component failure
The IO Accelerator is a highly fault-tolerant storage subsystem that provides many levels of protection against component failure and the loss nature of solid state storage. However, as in all storage subsystems, component failures might occur.
By pro-actively monitoring device age and health, you can ensure reliable performance over the intended product life.
Health metrics
The IO Accelerator manages block retirement using pre-determined retirement thresholds. The HP IO Accelerator Management Tool and the fio-statusutilities show a health indicator that starts at 100 and counts down to 0. As certain thresholds are crossed, various actions are taken.
At the 10% healthy threshold, a one-time warning is issued. For more information, see "Health monitoring techniques."
At 0%, the device is considered unhealthy. It enters write-reduced mode, which somewhat prolongs its lifespan so data can be safely migrated off. In this state the IO Accelerator device behaves normally, except for the reduced write performance.
After the 0% threshold, the device will soon enter read-only mode, and any attempt to write to the IO Accelerator device causes an error. Some filesystems might require special mount options to mount a read-only block device in addition to specifying that the mount must be read-only.
For example, under Linux, ext3 requires that -o ro, noload is used. The noload option tells the filesystem to not try and replay the journal.
Consider the read-only mode as a final opportunity to migrate data off the device, as device failure is more likely with continued use.
The IO Accelerator device might enter failure mode. In this case, the device is offline and inaccessible. This can be caused by an internal catastrophic failure, improper firmware upgrade procedures, or device wearout.
The IO Accelerator driver manages LEB retirement via use of pre-determined retirement thresholds. The IO Accelerator Management Tool and the fio-statusutility show a health indicator that starts at 100 and counts down to 0. As certain thresholds are crossed, various actions are taken.
At the 10% healthy threshold, a one-time warning is issued. For more information, see "Health monitoring techniques."
At 0%, the device is considered unhealthy. It enters write-reduced mode, which somewhat prolongs its lifespan so data can be safely migrated. In this state, the IO Accelerator behaves normally except for the reduced write performance.
At some point after the 0% threshold, the device enters read-only mode. Any attempt to write to the IO Accelerator causes an error. Some file systems might require special mount options to mount a read-only
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