6.21 Using NLVM with Linux Software RAIDs

Linux Software RAIDs are intended to be used with Linux tools and file systems. Consider the caveats in this section before implementing Linux Software RAIDS on your OES server.

6.21.1 Linux Software RAIDs

We recommend that you do not use Linux software RAIDs (such as MD RAIDs and Device Mapper RAIDs) for devices that you plan to use for storage objects that are managed by NSS management tools. The Novell Linux Volume Manager (NLVM) utility and the NSS Management Utility (NSSMU) list Linux software RAID devices that you have created by using Linux tools. Beginning with Linux Kernel 3.0 in OES 11 SP1, NLVM and NSSMU can see these devices, initialize them, and allow you to create storage objects on them. However, this capability has not yet been fully tested.

IMPORTANT:In OES 11, a server hang or crash can occur if you attempt to use a Linux software RAID when you create storage objects that are managed by NSS management tools.

For NSS pools, you can use hardware RAID devices or NSS Software RAID devices to achieve disk fault tolerance.

For Linux POSIX volumes, LVM volume groups, and cLVM volume groups, you can use hardware RAID devices on your storage subsystem to achieve disk fault tolerance.

6.21.2 Linux Software RAIDs Are Not Cluster Aware

Do not use Linux Software RAIDs for devices that you plan to use for shared storage objects. Linux Software RAID devices do not support concurrent activation on multiple nodes; that is, they are not cluster aware. They cannot be used for shared-disk storage objects, such as the OCFS2 file system, cLVM volume groups, and Novell Cluster Services SBD (split-brain-detector) partitions.

For shared disks, you can use hardware RAID devices on your storage subsystem to achieve fault tolerance.

6.21.3 Linux Software RAIDs Are Not Recommended for the System Device

We recommend that you do not use Linux software RAIDs (such as MD RAIDs and Device Mapper RAIDs) on the system device if you plan to use free space on the device later for storage objects managed by NSS tools. During the SLES and OES installation, if you create a Linux software RAID device to use as the system device for the root (/) file system, the free space on the system device cannot be used later for NSS pools because the configuration of NSS storage objects on Linux software RAIDs has not yet been fully tested.

IMPORTANT:In OES 11, a server hang or crash can occur if you attempt to use a Linux software RAID when you create storage objects that are managed by NSS management tools.

For the Linux system device, you can use a hardware RAID device to achieve fault tolerance. This allows NSS tools to see and use any available free space on the system device for unshared NSS pools.