Installation manual

49 ATTO Technology Inc. ATTO Utilities Installation and Operation Manual
Serious Disk Failure During Rebuild - Using
“Extreme” Mode
Exhibit 1.4.1--30 RAID 5 Group with 4 Operational
Drives
Exhibit 1.4.1--31 A drive Fails; RAID Group goes
DEGRADED
Exhibit 1.4.1--32 Drive is Removed and Replaced, and
Rebuild Starts
Exhibit 1.4.1--33 Second Unrecoverable Failure;
Rebuild Halts, RAID Group goes OFFLINE
Exhibit 1.4.1--34 Recover Extreme: All Drives Are Used
to Try to Recover Data
When a serious disk failure occurs during a rebuild,
the rebuild cannot be forced to continue, but the
Extreme recovery mode may be viable. If there is an
available slot, reinstall the original failed drive (the
drive provides another possible source of data even if
the data is stale). This original failed drive will only be
accessed if there is an error on one of the other RAID
Group members. Note that in this failure scenario,
data may be extensively compromised.
Extreme Recovery Mode is only accessible from the
Command Line Interface. Use the CLI command
RGRecover Extreme to enter the “extreme, read-at-
all-costs” recovery mode. Use a host application to
read the data (whatever you can) off of the drives and
back it up to another location. The RAID Group will
stay in recovery mode. If you use the CLI command
RGRecover Disable to disable this mode, the RAID
Group will return to the OFFLINE state. There is no
mechanism to put this RAID Group back online.
Once you have the data backed up, use only good
drives to create a new RAID Group, and then restore
the data to the new RAID Group.
Faults on Critical Number of Drives
Exhibit 1.4.1--35 RAID 5 Group with 4 Operational
Drives
Exhibit 1.4.1--36 A drive Fails; RAID Group goes
DEGRADED
Exhibit 1.4.1--37 A Media Error occurs; RAID Group
goes OFFLINE
In this scenario, there is no Hot Spare drive, and either
Auto Rebuild is not enabled or there is no spare drive
for Auto Rebuild to use. When the first drive fails, the
array will continue to operate in DEGRADED mode
and return data when requested. However, once
another error occurs, the array is OFFLINE and data
has been compromised. Basic recovery mode should
be used.
Basic Recovery Mode
CLI commands or the GUI can be used to put the
drives into basic recovery mode. This allows you to
read data to a backup location, replace all failed or
marginal drives, and then restore the data to the new
drives. However, at the location corresponding to the
Media Error, the data may be invalid! Anytime a RAID
Group goes OFFLINE, data integrity
has been
compromised
. It is imperative that data consistency
checks and file system repair tools are used to validate
the data.
To enter recovery mode from the ATTO ConfigTool,
select the Offline RAID Group and right-click to get the
menu options. Select the option Basic Rebuild as
shown below.
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4
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4
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4A
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4A
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4A 4
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