Chapter 6. Storage

iprutil support for SAS VRAID functions
The iprutils package provides utilities to manage and configure SCSI devices that are supported by the ipr SCSI storage device driver. The iprutils package has been updated to support SAS VRAID functions for new 6 GB SAS adapters on IBM POWER7.
LVM RAID support
In Red Hat Enterprise Linux 6.2, support for MD's RAID personalities has been added to LVM as a Technology Preview. The following basic features are available: create, display, rename, use, and remove RAID logical volumes. Automated fault tolerance is not yet available.
It is possible to create RAID logical volumes by specifying the --type <segtype> argument. The following are a few examples:
  • Create a RAID1 array (this is a different implementation of RAID1 than LVM's mirror segment type):
    ~]# lvcreate --type raid1 -m 1 -L 1G -n my_lv my_vg
  • Create a RAID5 array (3 stripes + 1 implicit parity):
    ~]# lvcreate --type raid5 -i 3 -L 1G -n my_lv my_vg
  • Create a RAID6 array (3 stripes + 2 implicit parity):
    ~]# lvcreate --type raid6 -i 3 -L 1G -n my_lv my_vg
iSCSI extension for RDMA (iSER) initiator and target
iSER initiator and target is now fully supported. Red Hat Enterprise Linux can now function as an iSCSI initiator and storage server in production environments that use InfiniBand and where high throughput and low latency are key requirements.
Reduced activation times for LVM devices
LVM devices can now be activated or deactivated quicker than before. This is relevant to high-density environments that involve a large number of LVM configurations. An example of this is a host that supports hundreds of virtual guests each using one or more logical volumes.
Support for raw ECKD access to the DASD driver
Normal I/O operations through the DASD device driver give access only to the data fields of an ECKD device even for track based I/O. In Red Hat Enterprise Linux 6.2, the DASD device driver is extended to give access to whole ECKD tracks including count, key, and data fields.