HP Storageworks 8100 - enterprise virtual array, User Manual

Page: 76 / 408

that
modprobe
could not find a driver for a particular combination of major and minor numbers. You
can ignore these messages, which occur when Linux is unable to find a driver to associate with a
SCSI device node that the iSCSI daemon is opening as part of the
symlink
creation process. To
prevent these messages from occurring, remove the SCSI device nodes that do not contain an associated
high-level SCSI driver.
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 if the driver is restarted repeatedly.
The bindings file ensures that the SCSI number in the
symlinks
device (described in
“ Device names ” on page 75) always maps to the same iSCSI target.
NOTE:
Linux dynamically allocates SCSI device nodes as SCSI devices are found; therefore, the driver cannot
ensure that a SCSI device node (for example,
/dev/sda
) always maps to the same iSCSI target
name. The
symlinks
described in “ Device names ” on page 75 provide application and
fstab
file
persistent device mapping; use these
symlinks
instead of direct references to SCSI device nodes.
If the bindings file grows too large, you can edit the file and remove the lines for targets that no longer
exist. This should not be necessary because the driver can maintain up to 65,535 bindings.
Mounting file systems
The Linux boot process typically mounts the file systems listed in
/etc/fstab
before the network is
configured; therefore, 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
/etc/
fstab.iscsi,
which has the same format as
/etc/fstab
. This script is invoked automatically 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 may time out and fail to mount the file systems.
Mapping inconsistencies can occur between SCSI device nodes and iSCSI targets (for example, the
wrong device is mounted because of device name changes resulting from iSCSI target configuration
changes or network delays). Instead of directly mounting SCSI devices, HP recommends that you do
one of the following:
• Mount the
/dev/iscsi symlink tree
.
• Mount the file system UUIDs or labels (see the man pages for
mke2fs
,
mount
, and
fstab
).
• Use the Logical Volume Manager (see Linux LVM).
Unmounting file systems
You must 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 may occur.
MPX200 iSCSI configuration rules and guidelines 76