Chapter 11. Administration - Tools
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Draft Document for Review August 30, 2007 12:59 am
7065Admin_Tools.fm
scan over host activity to ensure that the scan completes in the allocated time. This scan can
impact performance, but improve data integrity.
Media scan should be enabled for the entire storage subsystem. The system wide enabling
specifies the duration over which the media scan will run. The logical drive enabling specifies
whether or not to do a redundancy check as well as media scan.
A media scan can be considered a surface scan of the hard drives while a redundancy check
scans the blocks of a RAID 3 or 5 logical drive and compares it against the redundancy data.
In the case of a RAID 1 logical drive, then the redundancy scan compares blocks between
copies on mirrored drives.
The media scan function is designed to minimize its impact on other system I/O - in most
cases, no effect on I/O should be observed with a 30 day setting unless the processor is
utilized in excess of 95%. The length of time that it will take to scan the LUNs depends on the
capacity of all the LUNs on the system and the utilization of the controller. Table 11-1 shows
the possible errors and describes some of the actions that the DS3000 will take as a result of
media scan and redundancy check operations. The media scan reports any errors that are
found to the event log.
Table 11-1 Media scan errors
A media scan is a long running progress with lowest priority. So you can only run a media
scan on logical drives that meet the following conditions:
Optimal Status
No modification operation in progress
Change Media Scan Settings
Click Change Media Scan Settings (Figure 11-1 on page 246) to open the associated view
(Figure 11-8 on page 252).
Reported error
Description
Result
Unrecovered media
error
The data could not be read on
its first attempt, or on any
subsequent retries.
With redundancy check: data is
reconstructed and scanned again.
Without redundancy check: no error
correction.
Recovered media
error
The drive could not read the
requested data on its first
attempt, but succeeded on a
subsequent attempt.
Data is written to drive and verified.
Redundancy
mismatches
Redundancy errors are found.
The first 10 redundancy mismatches found
on a logical drive are reported. Operating
system data checking operations should
be executed.
Unfixable error
The data could not be read, and
parity or redundancy
information could not be used to
regenerate it.
Error is reported.
