HP 3000 Enterprise Virtual Array - Manual (Page 84)

Target bindings
The iSCSI driver automatically maintains a bindings file, /var/iscsi/bindings. This file contains
persistent bindings to ensure that the same iSCSI bus and target ID number are used for every iSCSI
session with a particular iSCSI TargetName, even when the driver is repeatedly restarted.
This feature ensures that the SCSI number in the device symlinks (described in “ Device
names ” on page 82) always map to the same iSCSI target.
NOTE:
Because of the way Linux dynamically allocates SCSI device nodes as SCSI devices are found, the
driver does not and cannot ensure that any particular SCSI device node /dev/sda, for example,
always maps to the same iSCSI TargetName. The symlinks described in “
Device
names ” on page 82 are intended to provide application and fstab file persistent device mapping
and must be used instead of direct references to particular SCSI device nodes.
If the bindings file grows too large, lines for targets that no longer exist may be manually removed
by editing the file. Manual editing should not be needed, however, since the driver can maintain up
to 65,535 different bindings.
Mounting file systems
Because the Linux boot process normally mounts file systems listed in /etc/fstab before the network
is configured, adding mount entries in iSCSI devices to /etc/fstab will not work. The
iscsi-mountall
script manages the checking and mounting of devices listed in the file /etc/
fstab.iscsi, which has the same format as /etc/fstab. This script is automatically invoked by
the iSCSI startup script.
NOTE:
If iSCSI sessions are unable to log in immediately due to network or authentication problems, the
iscsi-mountall
script can time out and fail to mount the file systems.
Mapping inconsistencies can occur between SCSI device nodes and iSCSI targets, such as mounting
the wrong device due to device name changes resulting from iSCSI target configuration changes or
network delays. Instead of directly mounting SCSI devices, HP recommends one of the following
options:
• Mount the /dev/iscsi tree symlinks.
• Mount file system UUIDs or labels (see man pages for mke2fs, mount, and fstab).
• Use logical volume management (see Linux LVM).
Unmounting file systems
It is very important to unmount all file systems on iSCSI devices before the iSCSI driver stops. If the
iSCSI driver stops while iSCSI devices are mounted, buffered writes may not be committed to disk,
and file system corruption can occur.
Since Linux will not unmount file systems that are being used by a running process, any processes
using those devices must be stopped (see fuser(1)) before iSCSI devices can be unmounted.
Setting up the iSCSI Initiator and storage 84