Red Hat ENTERPRISE 5.4 RELEASE NOTES, Manual

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iSER Support
iSER support, allowing for block storage transfer across a network, has been added to the
scsi-
target-utils
package as a Technology Preview. In this release, single portal and multiple
portals on different subnets are supported. There are known bugs when using multiple portals on
the same subnet.
To set up the iSER target component install the scsi-target-utils and libibverbs-devel RPM. The
library package for the InfiniBand hardware that is being used is also required. For example:
host channel adapters that use the
cxgb3
driver the
libcxgb3
package is needed, and for host
channel adapters using the
mthca
driver the
libmthca
package is needed.
There is also a known issue relating to connection timeouts in some situations. Refer to
Red Hat
Bugzilla #470627
21
for more information on this issue.
cman fence_virsh fence agent
The fence_virsh fence agent is provided in this release of Red Hat Enterprise Linux as a
Technology Preview. fence_virsh provides the ability for one guest (running as a domU) to fence
another using the libvirt protocol. However, as fence_virsh is not integrated with cluster-suite it is
not supported as a fence agent in that environment.
glibc new MALLOC behaviour
The upstream glibc has been changed recently to enable higher scalability across many sockets
and cores. This is done by assigning threads their own memory pools and by avoiding locking
in some situations. The amount of additional memory used for the memory pools (if any) can be
controlled using the environment variables MALLOC_ARENA_TEST and MALLOC_ARENA_MAX.
MALLOC_ARENA_TEST specifies that a test for the number of cores is performed once the
number of memory pools reaches this value. MALLOC_ARENA_MAX sets the maximum number
of memory pools used, regardless of the number of cores.
The glibc in the RHEL 5.4 release has this functionality integrated as a Technology Preview
of the upstream malloc. To enable the per-thread memory pools the environment variable
MALLOC_PER_THREAD needs to be set in the environment. This environment variable will
become obsolete when this new malloc behaviour becomes default in future releases. Users
experiencing contention for the malloc resources could try enabling this option.
21
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=470627