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EMC Symmetrix DMX-3 Product Guide
Data Integrity, Availability, and Protection
Figure 45 Reading data in RAID 5 normal mode
Regeneration
RAID 5 regeneration contains the following principles:
◆ “Data recovery with RAID 5” on page 202
◆ “RAID 5 recovery with a dynamic spare or permanent spare” on
page 203
◆ “Write requests during regeneration” on page 203
◆ “Read requests during regeneration” on page 203
◆ “Fast Copy Back after replacing a disk using dynamic sparing”
on page 203
Data recovery with
RAID 5
Symmetrix RAID 5 provides continuous availability for all data if any
single physical disk in the RAID 5 device fails or becomes
unavailable. If a media error occurs, the affected tracks are
regenerated. When a device fails or becomes unavailable, the
Symmetrix RAID 5 device is put in regeneration mode. All data is still
available to the host, but is unprotected against additional failures
unless protected by dynamic sparing or permanent sparing.
A four-track stripe of parity
A stripe of four tracks of data
Write requires parity to be updated.
Reads can occur simultaneously on every drive.
SYM-000727
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