Quorum Disks - IBM Storwize V5010 Manual

Array
Array mode MDisks are constructed from internal drives by using the RAID functionality.
Array MDisks are always associated with storage pools.
Unmanaged
LUNs that are presented by external storage systems to IBM Storwize V5000 Gen2 are
discovered as unmanaged MDisks. The MDisk is not a member of any storage pools,
which means that it is not used by the IBM Storwize V5000 Gen2 storage system.
Managed
Managed MDisks are LUNs, which are presented by external storage systems to an IBM
Storwize V5000 Gen2, that are assigned to a storage pool and provide extents so that
volumes can use them. Any data that might be on these LUNs when they are added is
lost.
Image
Image MDisks
Storwize V5000 Gen2 and assigned directly to a volume with a one-to-one mapping of
extents between the MDisk and the volume. For more information, see Chapter 6, "Volume
configuration" on page 287.

1.6.7 Quorum disks

quorum disk
A
the IBM Storwize V5000 Gen2, internal drives can be considered as quorum candidates. The
clustered system uses quorum disks to break a tie when exactly half the nodes in the system
remain after a SAN failure.
The clustered system automatically forms the quorum disk by taking a small amount of space
from an MDisk. It allocates space from up to three different MDisks for redundancy, although
only one quorum disk is active.
To avoid the possibility of losing all of the quorum disks because of a failure of a single
storage system if the environment has multiple storage systems, you need to allocate the
quorum disk on different storage systems. You can manage the quorum disks by using the
CLI.
IP quorum base support provides an alternative for Storwize V5000 IBM HyperSwap®
implementations. Instead of Fibre Channel storage on a third site, the IP network is used for
communication between the IP quorum application and node canisters in the system to cope
with tie-break situations if the inter-site link fails. The IP quorum application is a Java
application that runs on a host at the third site. The IP quorum application enables the use of
a lower-cost IP network-attached host as a quorum disk for simplified implementation and
operation.
Note: IP Quorum allows the user to replace a third-site Fibre Channel-attached quorum
disk with an IP Quorum application. The Java application runs on a Linux host and is used
to resolve split-brain situations. Quorum disks are still required in sites 1 and 2 for cookie
crumb and metadata. The application can also be used with clusters in a standard
topology configuration, but the primary use case is a customer with a cluster split over two
sites (stretched or HyperSwap).
You need Java to run the IP quorum. Your Network must provide as least < 80 ms
round-trip latency. All nodes need a service IP address, and all service IP addresses must
be pingable from the quorum host.
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Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
are LUNs that are presented by external storage systems to an IBM
is an MDisk that contains a reserved area for use exclusively by the system. In