IBM 86655RY - Netfinity 7600 - 8665, Руководство по техническому обслуживанию аппаратной части

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Hardware Maintenance Manual: Netfinity 7600 – Type 8665 Models 1RY, 2RY
• By reading every file on the disk, the backup process forces the disk and the
controller to discover any sector media errors and to correct them, greatly
decreasing the likelihood of the rebuild failures described in the previous section.
If weekly tape backups are performed, data scrubbing is still recommended to
detect and correct sector media errors in non-data areas of the drives.
If a sector media error has not been discovered and an array rebuild fails as described
previously, a full tape backup can then be performed to minimize data loss. The tape
backup saves all files except for the one containing the damaged sector. The drives can
then be restored from the configuration disk and synchronized, forcing the remapping
of bad sectors. The data can then be restored. The files that were contained on the
damaged sector would then have to be restored from a prior backup.
Automatic Data scrubbing: Automatic data scrubbing continuously reads all sectors of
all logical drives in the background while the system is running. If a defective sector is
found, it is automatically repaired. The advantage to this procedure, when used in
addition to tape backups, is that data scrubbing examines unallocated sectors of the
drive, in addition to those that have been allocated, that is, data areas protected by a
tape backup. If any sector media errors are found during this process, they are
corrected at the disk level using disk ECC information, if possible, or at the array level
using RAID parity information, if necessary. Automatic data scrubbing is enabled by
defaults.
Note: You do not need to synchronize RAID level-0 or 1 logical drives before storing
data.
Data scrubbing continuously reads all sectors of RAID-1 and RAID-5 logical drives in
the background while the system is running. If a defective sector is found, it is
automatically repaired. As a result of this feature, you no longer have to synchronize
logical drives on a weekly basis.
Acronyms, terms, and definitions
Acronyms and terms are listed in alphabetical order in the following table.
array An arrangement of data in one or more dimensions: a list, a table, or a
multidimensional arrangement of items. In the ServeRAID environment, data
is striped across multiple physical hard drives. The array is defined as the set
of hard drives included in the data striping.
block A string of data elements recorded or transmitted in a unit. The elements may
be characters, words, or physical records.
byte A string of eight bits that is treated as a unit, and that represents a character.
cache memory
A special buffer storage, smaller and faster than main storage, that is used to
hold a copy of instructions and data in main storage that are likely to be
needed next by the processor, and that have been obtained automatically
from main storage.
CDR CD-ROM
CRT Critical
DASD Direct access storage device.
Data Scrubbing
The process that forces all data sectors in a logical drive to be accessed so that
sector media errors are identified and corrected at the disk level using disk
ECC information, if possible, or at the array level using ServeRAID parity
information, if necessary. For a high level of data protection, perform data
scrubbing weekly.