Considerations For Replacing Existing Storage; Reformatting Disk Drive Modules On Open Systems - IBM DS8000 User Manual

v Management software provides simple robust methods that you can generally
v The AIX logical volume manager (LVM) provides methods that you can use at
v Methods that use backup and restore procedures generally have the most impact

Considerations for replacing existing storage

There are various factors to consider (remapping, reformatting of disk drives,
partitioning) when replacing existing storage.
When you are replacing existing storage, partition the storage so that its virtual
disks are similar in configuration to the disk drives that they are replacing. New
configurations must be large enough to accommodate the existing data.
Note: You might want to take advantage of this opportunity to do some

Reformatting disk drive modules on open systems

To provide integrity-checking of data and to allow different operating systems to
use the storage unit, IBM formats storage unit disks to a 524-byte sector.
The 524-byte sector replaces the traditional 512-byte sector of fixed-block
architecture disk drive modules (DDMs). The 524-byte sector format requires that
you reformat all disks that you are migrating to the storage unit. Because
reformatting will erase any data that is already contained on the drives, you must
back up the data to some form of temporary storage.
You can use the DDM for either direct migration of data or as temporary storage
while the existing drives are moved. If this is not possible, use a removable media
device such as a tape drive to temporarily store the data while you reformat the
drives.
The AIX LVM uses a fixed-byte sector of 512-bytes. When used in a storage unit,
the format is a fixed-byte sector of 524-bytes. The data portion of the sector
remains at 512-bytes. System i headers use eight additional bytes. A 2-byte
sequence number and a 2-byte longitudinal redundancy check (LRC) complete the
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DS8000 User's Guide
use during production without disturbing users.
any time without disrupting user access to the data. You might notice a small
performance degradation, but this is preferable to shutting down databases or
requiring users to log off the system.
Notes:
– AIX and HP-UX 11.xx ship with logical volume management (LVM)
software as part of the base operating system. LVM provides complete
control over all disks and file systems that exist on an AIX system.
HP-UX has similar volume management software.
– Sun Microsystems has a basic volume management product called
Solstice, which is available for the Solaris systems.
– Linux systems also use the LVM.
on the system usage. They require that databases and file systems be in
quiescent states to ensure a valid snapshot of the data.
remapping. The allocation and distribution of data does not have to be a
straight one-to-one relationship, although that is possible. For instance, you
can take advantage of using a maximum of 255 logical subsystems whereas
the prior limitation was 32 logical subsystems.