HP EVA P6000 Storage - Manual (Page 114)

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
“Assigning device names” (page 112) 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.
To avoid file system corruption, the iSCSI shutdown script automatically stops all processes using
devices in /etc/fstab.iscsi, first by sending them SIGTERM, and then by sending any
remaining processes SIGKILL. The iSCSI shutdown script unmounts all iSCSI file systems and stops
the iSCSI daemon, terminating all connections to iSCSI devices.
CAUTION: File systems not listed in /etc/fstab.iscsi cannot be automatically unmounted.
114 iSCSI or iSCSI/FCoE configuration rules and guidelines