2.5. Storage and File Systems

Multipath's queue_without_daemon yes default option queues I/O even though all iSCSI links have been disconnected when the system is shut down, which causes LVM to become unresponsive when scanning all block devices. As a result, the system cannot be shut down. To work around this issue, add the following line into the defaults section of /etc/multipath.conf:

queue_without_daemon no

If the /etc/fstab file contains an NFS mount entry that has the file system check (fsck) enabled, the netfs service responsible for mounting and unmounting NFS file systems initializes the file system check. Because NFS is not a block-level file system, this operation fails, and subsequently also fails the system boot itself. To work around this problem, disable the file system check by setting the sixth vaule for NFS mount entries to 0.

iSCSI discovery via a TOE (TCP Offload Engine) interface fails when the iscsiadm -m iface has never been executed. This is due to the iscsiadm -m discovery command not checking interface settings while the iscsiadm -m iface does. To work around this issue, run the iscsiadm -m iface command at least once after installing the iscsi-initiatio-utils package. Once the interface setting is updated, discoveries are performed with no errors.

Attempting to create/extend a storage domain on/with a device that exposes a block size different than 512 bytes such create/extend request to fail. To work around this issue, the storage must be configured to expose a block size of 512 bytes.

The NFSv4 server in Red Hat Enterprise Linux 6 currently allows clients to mount using UDP and advertises NFSv4 over UDP with rpcbind. However, this configuration is not supported by Red Hat and violates the RFC 3530 standard.

The dracut utility currently only supports one FiberChannel over Ethernet (FCoE) connection to be used to boot from the root device. Consequently, booting from a root device that spans multiple FCoE devices (for example, using RAID, LVM or similar techniques) is not possible.

The pvmove command cannot currently be used to move mirror devices. However, it is possible to move mirror devices by issuing a sequence of two commands. For mirror images, add a new image on the destination PV and then remove the mirror image on the source PV:

~]$ lvconvert -m +1 <vg/lv> <new PV>
~]$ lvconvert -m -1 <vg/lv> <old PV>

Mirror logs can be handled in a similar fashion:

~]$ lvconvert --mirrorlog core <vg/lv>
~]$ lvconvert --mirrorlog disk <vg/lv> <new PV>

or

~]$ lvconvert --mirrorlog mirrored <vg/lv> <new PV>
~]$ lvconvert --mirrorlog disk <vg/lv> <old PV>