Compex Systems Advanced SerialRAID Adapters SA33-3285-02 User Manual
Page 169
Chapter 7. Copying Data from Arrays and from Volume Groups
When disk drives are configured through the Logical Volume Manager for mirroring, you
can use the Split Copy function to create a copy of a logical volume. You can then save
that copy on a tape or other medium for backup purposes. When disk drives are
configured as members of a RAID-1 or RAID-10 array, a similar function, called 3-Way
Copy, is available. This chapter describes the 3-Way Copy function, and how it can be
used. It does not describe the Split Copy function of the Logical Volume Manager.
Note: The 3-Way Copy function is available only with adapter microcode level A000 or
above.
The 3-Way Copy procedure allows you to create a separate copy of an hdisk, of a
complete volume group, or of part of a volume group. The copy is prepared on a
separate disk drive for a RAID-1 array, or on several disk drives for a RAID-10 array.
You cannot use the 3-Way Copy procedure for RAID-5 arrays, for RAID-0 arrays, or for
non-RAID disk drives, whether or not they are configured for Logical Volume mirroring.
When the copy has been prepared, and the copy operation is complete, the copy
remains synchronized with the parent. It can be uncoupled later. The uncoupled copy is
renamed from the original name so that it can be separately accessed after it is
uncoupled.
If the RAID-1 arrays or RAID-10 arrays are used as raw hdisks, you control the 3-Way
Copy function from SMIT menus or from ssaraid commands. Facilities are provided that
allow you to identify suitable candidate disk drives for the copy and to couple those disk
drives to the parent array. By using SMIT menus or an ssaraid command, you can
uncouple the copy from the parent array; the uncoupled array becomes a new hdisk.
Before the copy is uncoupled, all fast-write data is destaged to the array. Data held in a
system cache that has not yet been sent to the adapter must be flushed before the
uncouple operation.
If the RAID-1 or RAID-10 array is used to hold logical volumes, you can use the
ssa_make_copy command to make and uncouple a copy of the complete logical
volume group, or of part of a logical volume group. This command:
v
Selects disk drives for the copy operation
v
Synchronizes data from system cache memory to the array
v
Copies the required logical volume group, logical volume, or file system to the copy
disk drives
v
Uncouples the copy disk drives from the parent array
v
Renames the volume group and logical volumes
The complete procedure for synchronizing the data, copying to separate disk drives,
and uncoupling the copy can therefore be done from a single command. You can use
SMIT menus or ssaraid commands to copy and uncouple RAID-1 and RAID-10 arrays
that hold logical volumes, as you do for raw hdisks. SMIT commands or ssaraid
commands, however, operate only on whole hdisks. If you use these commands, you
must ensure, in a separate operation, that all cached data in system memory has been
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