Product manual

CDA 7 5630 Product Manual
5-16 77 A1 69UP Rev00
5.5.3 Error Recovery with Mirroring
Should one volume in the mirrored pair fail, CDA 7 automatically uses the other
volume without interruption. CDA 7 notifies the Bull Competence Center of this
condition. When the defective device containing the volume is replaced, CDA 7
re-establishes the mirrored pair and automatically copies data to the new disk.
During the copy operation, CDA 7 gives priority to host I/O requests over copying
to minimize the effect on performance. All new writes take place to both devices.
The time it takes to resynchronize the mirrored pair depends on the I/O activity to
the volume, the disk device, and the disk capacity.
5.5.4 Mirroring Advantages
In summary, mirroring offers the following advantages:
• Improved performance over traditional RAID 1 by supporting 100 percent fast
write, and two simultaneous internal data transfer paths.
• Protection of mission-critical data from any single point of failure.
• Continuous business operation by switching to the alternate disk device of a
mirrored pair without interruption to data availability should loss of access occur
to one of the disk devices in a mirrored pair.
• Assurance that the second copy of data is identical to the first copy.
• Automatic resynchronization of the mirrored pair after repair of the defective
volume.
5.6 SRDF for GCOS 7
The SRDF for GCOS 7 Solution is aimed at providing a complete business
continuance capability during the unlikely event of a data center disaster.
SRDF for GCOS 7 is based on CDA 7 SRDF mechanism allowing for a physical
remote copy of disk volumes and operating
• in campus mode with ESCON-compliant fiber optics link or high speed data
lines,
• in synchronous mode for a full logical synchronisation of mirrored volumes,
• with the two involved CDA 7’s configured in RAID-1.