22 Dell Compellent Using Storage Center with FCoE and Linux
Instead of using LVM, a file system will simply be laid across the entire volume. For more information
about LVM and Storage Center, please consult the Linux Best Practices paper.
# mkfs.xfs /dev/mapper/mpathiscsivol01
log stripe unit (2097152 bytes) is too large (maximum is 256KiB)
log stripe unit adjusted to 32KiB
meta-data=/dev/mapper/mpathiscsivol01 isize=256 agcount=33, agsize=83885568 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=2684354560, imaxpct=5
= sunit=512 swidth=512 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=521728, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Finally, a mount point and fstab entry has to be created, and the volume mounted. Notice the “_netdev”
mount flag that is entered into the fstab file, this ensures that no attempt to mount the file system is made
till the network is brought up and the iSCSId daemon has been started at boot time.
# mkdir /var/backups
# echo "/dev/mapper/mpathiscsivol01 /var/backups/ xfs _netdev,noatime 0 0" >>
/etc/fstab & mount –a
The configuration is now complete, the Linux server is now accessing storage presented by two different
Storage Centers using two storage protocols all across one converged logical network.
1.3 Special considerations
By default, if an Fibre Channel HBA and a FCoE CNA from the same vendor are installed on the same
physical host, it is likely that they will share a common driver (qla2xxx for example). This may potentially
cause problems if the connectivity has different characteristics, both performance and especially topology
characteristics. For example, if the Fibre Channel connectivity provides multiple paths, but the FCoE
connectivity does not, then the timeout values for the driver will need to be set high, in order to allow the
non-multipath managed volumes to survive Storage Center failover events. This sort of dilemma can be
overcome in multiple ways. Some examples are to have Linux multipath manage all volumes regardless of
the absence of multiple paths, and use the “queue_if_no_path” flag to guarantee surviving Storage Center
controller failovers. Another example is by the use of the hardware model specific proprietary drivers,
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