Table of Contents
Advertisement
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 an storage unit,
the format is a fixed-byte sector of 524-bytes. The data portion of the sector
remains at 512-bytes. AS/400 and iSeries headers use eight additional bytes. A
2-byte sequence number and a 2-byte longitudinal redundancy check (LRC)
complete the extra bytes. The storage unit LIC uses the sequence number and
LRC. The storage unit does not transfer them to the host system.
Most fixed-block disk architectures use a fixed-byte sector of 512-bytes. This
includes most UNIX systems, including AIX. When used in an storage unit, the
format of a DDM has a fixed–byte sector of 524-bytes. The 524-byte sector format
enables the storage unit to connect to a wide range of host systems and share data
between them.
The 524-byte sector on the DDM is independent of the sector size exposed to the
host for a given device type emulation. Most LUNs for open-systems hosts are
exposed with a 512-byte sector.
The IBM AS/400 and iSeries host systems use eight bytes at the start of the sector.
UNIX host systems do not use these eight bytes when you attach them to the
storage unit. The data portion of the sector remains at 512-bytes for all host
systems. A 2-byte sequence number and a 2-byte LRC increase the size of the
sector to 524-bytes.
Overview of the logical volume management software
The logical volume manager (LVM) software migrates data at a single logical
volume level, a physical volume (DDM) level, or entire contents of a volume group.
The LVM software provides complete control over all disks and file systems.
The primary tasks involved in migrating data using the LVM rely upon the use of
LVM commands that affect the following functions:
v Copying
v Mirroring
v Migrating
Direct copy is another method to migrate data. While this method uses LVM, its
main focus is on the use of the UNIX find command and the cpio command.
Copying a complete logical volume
Use this information as a guide for using the logical volume manager (LVM) cplv
command to copy a complete logical volume.
The AIX LVM provides the cplv command for copying logical volumes within volume
groups or to different volume groups. You can use this command to create a new
logical volume while running the command, or you can overwrite an existing logical
volume. The following two examples shows how to use the cplv command.
Chapter 9. Migrating data to a storage unit
129
Advertisement
Table of Contents
