Flexible Storage Sharing (FSS) enables network sharing of local storage, cluster wide. The local storage can be in the form of Direct Attached Storage (DAS) or internal disk drives. Network shared storage is enabled by using a network interconnect between the nodes of a cluster.
FSS allows network shared storage to co-exist with physically shared storage, and logical volumes can be created using both types of storage creating a common storage namespace. Logical volumes using network shared storage provide data redundancy, high availability, and disaster recovery capabilities, without requiring physically shared storage, transparently to file systems and applications.
FSS is supported for CVM protocol versions 140 and above.
Figure: Flexible Storage Sharing Environment shows a Flexible Storage Sharing environment.
The following list includes several use cases for which you would want to use the FSS feature:
Note the following limitations for using Flexible Storage Sharing (FSS):
FSS is only supported on clusters of up to 8 nodes.
Disk initialization operations should be performed only on nodes with local connectivity to the disk.
FSS does not support the use of boot disks, opaque disks, and non-VxVM disks for network sharing.
Hot-relocation is disabled on FSS disk groups.
The vxresize operation is not supported on volumes and file systems from the slave node.
FSS does not support non-SCSI3 disks connected to multiple hosts.
Dynamic Lun Expansion (DLE) is not supported.
FSS only supports instant data change object (DCO), created using the vxsnap operation or by specifying "logtype=dco dcoversion=20" attributes during volume creation.
By default creating a mirror between SSD and HDD is not supported through vxassist, as the underlying mediatypes are different. To workaround this issue, you can create a volume with one mediatype, for instance the HDD, which is the default mediatype, and then later add a mirror on the SSD.
For example:
# vxassist -g diskgroup make volume size init=none
# vxassist -g diskgroup mirror volume mediatype:ssd
# vxvol -g diskgroup init active volume