HP StorageWorks Storage Mirroring for Linux User's Guide (T2558-96317, June 2009)

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1.3. Configure File System or Block Device Replication—Storage Mirroring hooks
operations for replication by interjecting itself between the kernel VFS layer and the
underlying file system. This must be done on a case by case basis for each block
device, mount point, or parent directory that needs to be replicated.
1.3.1. Configure File System Replication setup file—In order to use Storage
Mirroring replication, data that will be replicated must reside on a partition,
which is specially mounted with the Storage Mirroring file system (DTFS) driver.
DTFS is a transparent file system that monitors the storage file system so that
data changes can be captured. The data on those mount points can only be
replicated if they are under DTFS mount points. The DTSetup utility allows you
to configure entries in /etc/DT/dtfs_mounts to mount specific partitions as DTFS
when Storage Mirroring is started.
1.3.1.1. Add an entry to /etc/DT/dtfs_mounts—Type the path of the
highest subdirectory for which replication should be captured. This can
be the path to a mount point or a subdirectory of a volume. You can
either stop and restart the Storage Mirroring daemon so that new
entries in /etc/DT/dtfs_mounts will take effect or you can mount the
entries immediately using menu option 1.3.1.3.
1.3.1.2. Remove an entry from /etc/DT/dtfs_mounts—Type the path of
the entry that needs to be removed.
1.3.1.3. Mount all entries in /etc/DT/dtfs_mounts as DTFS—This option
will cause the entries of the list to be mounted with DTFS immediately,
rather than when the daemon is started. This allows you to review the
effects of the changes and troubleshoot any issues.
1.3.1.4. Unmount DTFS from all entries in /etc/DT/dtfs_mounts—This
will unmount DTFS from the mount points on the system, if any. This
allows you to make changes to the DTFS mounts without unloading the
daemon.
NOTE: When making changes replication configuration changes, stop any
applications that may be running and restart them after the replication
changes have been made. Storage Mirroring needs to be loaded on the file
system before any applications, otherwise some data may not be replicated.
NOTE: Storage Mirroring is compatible with NFS and Samba services as long
as they are mounted on top of Storage Mirroring. Storage Mirroring
should be mounted just above the storage file system. Additionally,
NFS and/or Samba must be started after the Storage Mirroring
daemon.
Do not select the root as a replication mount point.
If you have a single drive system, mount DTFS to any of the
subdirectories directly under root that you want to replicate.
NOTE: You will be prompted whether you want to replicate access
times. The access-time file property changes during a mirror
and causes replication operations to be generated during a
mirror and every time a file is read from or written to. This
may have a negative effect on performance. If you do not
replicate access times on both the source and target when
the volume is initially mounted, you may increase the
performance, especially during mirroring. (Access times
from files closes are always replicated regardless of this
configuration.)
NOTE: If you are using Konquerer, you can only unmount a
replication mount point by rebooting the server.