Installation manual

41 ATTO Technology Inc. ATTO Utilities Installation and Operation Manual
Data Recovery for OFFLINE RAID Groups
ATTO SAS/SATA RAID storage controllers use DriveAssure™ to maintain error-free operation of RAID
Group member drives. This includes features like Drive Initialization, Media Scan, Parity Verify,
Performance Monitoring, and algorithms for latency and response management. Occasionally, a drive will
suffer a mechanical or fatal media error that makes it unusable. A connection error may cause multiple
drives to be inaccessible, resulting in an array that cannot be accessed normally. This document describes
procedures to follow that may allow data to be partially recovered when drives fail or become inaccessible
and cause the ATTO RAID Group to go OFFLINE.
Note
Anytime a RAID Group goes OFFLINE, data integrity may be compromised (unless the conversion was
halted by the user). It is imperative that data consistency checks and/or file system repair tools are used
to validate recovered data.
Definitions
Exhibit 1.4.1--15 RAID Group Status Definitions
RAID Group Status Definition
ONLINE
The RAID Group state is ONLINE for RAID Groups with all members
available and fully operational.
DEGRADED
RAID Group does not have full data protection. This is the case when a
non critical number of RAID Group Members are UNAVAILABLE,
DEGRADED or FAULTED (i.e., 1 member in a RAID5 Group, 2 in a
RAID6 Group, and so forth). On a READ command to inaccessible
drive(s), the data is derived using redundancy or parity. A DEGRADED
RAID Group may be initializing or rebuilding.
OFFLINE
RAID Group data cannot be accessed because a critical number of drives have
FAULTED or been removed. For RAID 5, for example, two or more drives have
failed.
RECOVERY BASIC
RAID Group is in BASIC data recovery mode. I/O may be limited to
reads.
RECOVERY EXTREME RAID Group is in EXTREME data recovery mode, which returns data at
all costs. I/O may be limited to reads.
WAITING
The transient state of a group while it is being discovered.
DELETED
The transient state of a group while it is being deleted.
NEW
The state of a group that has been created but not yet committed.