The udev daemon in Red Hat Enterprise 6 watches all devices for changes. If a change occurs, the device is rescanned for device information to be stored in the udev database.

The scanning process causes additional I/O to devices after they were changed by tools. udev to can be told to exclude devices from being watched with a udev rule. A rule can be created by adding a new file <myname>.rules in /etc/udev/rules.d containing the following line:

ACTION=="add|change", SYMLINK=="disk/by-id/scsi-SATA_SAMSUNG_HD400LDS0AXJ1LL903246", OPTIONS+="nowatch"

The SYMLINK should be replaced with any symlink path found in /dev/disk/* for the device in question.

This will prevent unexpected I/O on the device, after data was written directly to the device (not on the filesystem). However, it will also prevent device updates in the udev database, like filesystem labels, symbolic links in /dev/disk/*, etc.

Under some circumstances, the bfa-firmware package in Red Hat Enterprise Linux 6 may cause these devices to encounter a rare memory parity error. To work around this issue, to update to the newer firmware package, available directly from Brocade.

Red Hat Enterprise Linux 6 only has support for the first revision of the UPEK Touchstrip fingerprint reader (USB ID 147e:2016). Attempting to use a second revision device may cause the fingerprint reader daemon to crash. The command

lsusb -v -d 147e:2016 | grep bcdDevice

will return the version of the device being used in an individual machine.

The Emulex Fibre Channel/Fibre Channel-over-Ethernet (FCoE) driver in Red Hat Enterprise Linux 6 does not support DH-CHAP authentication. DH-CHAP authentication provides secure access between hosts and mass storage in Fibre-Channel and FCoE SANs in compliance with the FC-SP specification. Note, however that the Emulex driver (lpfc) does support DH-CHAP authentication on Red Hat Enterprise Linux 5, from version 5.4. Future Red Hat Enterprise Linux 6 releases may include DH-CHAP authentication.

Partial Offload iSCSI adapters do not work on Red Hat Enterprise Linux. Consequently, devices that use the be2iscsi driver cannot be used during installation.

The hpsa_allow_any kernel option allows the hpsa driver to be used with older hardware that typically uses the cciss module by default. To use the hpsa driver with older hardware, set hpsa_allow_any=1 and blacklist the cciss module. Note, however that this is an unsupported, non-default configuration.

Platforms with BIOS/UEFI that are unaware of PCI-e SR-IOV capabilities may fail to enable virtual functions

The recommended minimum HBA firmware revision for use with the mpt2sas driver is "Phase 5 firmware" (i.e. with version number in the form 05.xx.xx.xx.) Note that following this recommendation is especially important on complex SAS configurations involving multiple SAS expanders.

The persistent naming of devices that are dynamically discovered in a system is a large problem that exists both in and outside of kdump. Nominally, devices are detected in the same order, which leads to consistent naming. In cases where devices are not detected in the same order, device abstraction layers (e.g. LVM) make essentially resolve the issue, though the use of metadata stored on the devices to create consistency. In the rare cases where no such abstraction layer is in use, and renaming devices causes issues with kdump, it is recommended that devices be referred to by disk label or UUID in kdump.conf.

The following issues and limitations may be encountered with the Broadcom bnx2, bnx2x, and cnic drivers