Mirror Write Consistency (MWC) ensu

Mirror Write Consistency (MWC) ensures data consistency on logical volumes in case a system crash occurs during mirrored writes.
The active method achieves this by logging when a write occurs.
LVM makes an update to the MWC log that identifies what areas of the disk are being updated before performing the write of the data.
Records of the last 62 distinct logical transfer groups (LTG)
written to disk are kept in memory and also written to a separate checkpoint area on disk (MWC log).
This results in a performance degradation during random writes.
With AIX 5L V5.1 and later, there are two ways of handling MWC:
- Active, the existing method (prior to AIX 5L V5.1)
- Passive, the new method (beginning with AIX 5L V5.1)