User guide

Monitoring, Maintenance, and Troubleshooting Features
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RAID 0 unit members. If the disk drive is part of a redundant unit, error
locations that are found and are deemed repairable are rewritten with the
redundant data. This forces the drive firmware to reallocate the error
sectors accordingly. (For more information, see “About Verification” on
page 146.)
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Error Correction. Bad sectors can be dynamically repaired through error
correction (Dynamic Sector Repair). Reallocation of blocks is based
intelligently on the location of the block in relation to the stripe.
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Scheduled Background Tasks. Initialize, rebuild, verify, and self-test
tasks can all be run in the background, at scheduled times. This lets you
choose a time for these tasks to be run when it will be least disruptive to
your system. You can also define the rate at which background tasks are
performed, specifying whether I/O tasks should be given more processing
time, or background rebuild and verify tasks should be given more
processing time. (For more information, see “Scheduling Background
Tasks” on page 156.)
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Write Cache. Write cache can be enabled or disabled using 3BM 2,
3DM 2 and CLI. When write cache is enabled, data will be stored in
system cache, 3ware controller cache, and drive cache before the data is
committed to disk. This allows the system to process multiple write
commands at the same time, thus improving performance. However when
data is stored in cache, it could be lost if a power failure occurs. With a
Battery Backup Unit (BBU) installed, the cache stored on the 3ware
controller can be restored. (For more information, see “Enabling and
Disabling the Unit Write Cache” on page 108.)
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StorSave™ Profiles allow you to set the level of protection versus
performance that is desired for a unit when write cache is enabled. (For
more information, see “Setting the StorSave Profile for a Unit” on
page 112.)
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Drive and Unit Identification. Units or drives in enclosures can be
identified by flashing LEDs. When the I
2
C port on the controller has been
connected to a chassis with a Chassis Control Unit (CCU), such as the
3ware Sidecar, you can issue drive Locate commands that blink the LEDs
for particular drives, so that you can quickly identify which drive needs to
be checked or replaced. For more information, see “Locating a Drive by
Blinking Its LED” on page 161.
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Auto Rebuild. For times when you do not have a spare available, setting
the Auto Rebuild policy allows rebuilds to occur with an available drive
or with a failed drive. (For more information, see “Setting the Auto
Rebuild Policy” on page 85.)