LSI SAS2 Integrated RAID Solution, User Manual

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Chapter 2: Overview of Integrated RAID Mirrored Volumes
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Operation of Mirrored Volumes SAS2 Integrated RAID Solution User Guide
Page 8 LSI Corporation Confidential
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August 2010
 Ability of mirrored volumes to run in optimal mode or in degraded mode if one
mirrored disk in an Integrated Mirroring volume fails or if one or more mirrored
disks fail in an Integrated Mir Striping volume or Integrated Mirroring
Enhanced volume.
 Support for hot swapping.
 Support for online capacity expansion (OCE) for RAID 1 volumes. OCE allows you to
increase the size of a RAID 1 volume by replacing the existing disk drives with
higher-capacity disk drives. Data is protected during the expansion process, and the
RAID 1 volume remains online.
 Presentation of a single, virtual drive to the operating system for each
mirrored volume.
 Support for both SAS and SATA disks, although you cannot combine the two types
of disks in the same volume. However, an LSI SAS2 controller can support one
volume with SATA disks and a second volume with SAS disks.
 Automatic background initialization after volume creation.
 Consistency checking.
 Fusion-MPT architecture.
 Menu-driven, BIOS-based configuration utility.
 Error notification, in which the drivers update an OS-specific event log.
 Support for SCSI Enclosure Services (SES) status LED.
 Write journaling, which allows automatic synchronization of potentially
inconsistent data after unexpected powerdown situations.
 Use of metadata to store volume configuration on disks in a mirrored volume.
 Automatic background resynchronization while host I/Os continue.
 Background media verification, which ensures that data on mirrored volumes is
always accessible.
2.3 Operation of Mirrored
Volumes
The LSI Integrated RAID solution supports one or two mirrored volumes on each LSI
SAS2 controller (or one mirrored volume and one Integrated Striping volume).
Typically, one of these volumes is the boot volume. Boot support is available through
the firmware of the LSI SAS2 controller that supports the standard Fusion-MPT
interface. The runtime mirroring of the boot disk is transparent to the BIOS, the drivers,
and the operating system. Host-based status software monitors the state of the
mirrored disks and reports any error conditions. The following figure shows an
Integrated Mirroring volume in which the second disk is a mirrored copy of the data on
the first (primary) disk.