586
Dell PowerConnect 55xx Systems User Guide
Limitations
The following limitations exist:
• All iSCSI connections receive the relevant QoS, regardless of whether they
are being monitored or not. If, for example, a feature was disabled for some
period and was enabled again, it is possible that there are iSCSI TCP
connections that were established during this period of time. These cannot
be monitored, because all relevant information was already passed at the
beginning of the session. But these unidentified sessions will still be
assigned to iSCSI QoS.
• The maximum number of iSCSI TCP connections, which is also the
default setting, is 1K. This can be changed after reset.
• The number of iSCSI connections affects other system features.
iSCSI-aware, DHCP Snooping, and ACL rules all use the TCAM system
resource. If the number of iSCSI connections has been increased, the
other application rules (DHCP Snooping or ACL) can be removed after
reset.
• If the target uses redirect messages upon the initiator request, and, as a
result, the initiator opens a connection to a different target, the new target
must be configured as part of the general configuration.
• Only iSCSI flows to targets that use the iSCSI well-known port or other
explicit user-defined configuration are assigned QoS.
• The aging configuration works for each connection. The mechanism
checks connection activities in a group of 28 TCP iSCSI connections,
within the aging time. In the worst case, when the maximum number of
1K TCP connections are monitored and are not terminated gracefully, the
mechanism causes inaccuracy, namely, the last 28 TCP iSCSI connections
are aged out after (1K/28)*aging-time.
• In general, the greater the number of ungracefully terminated iSCSI TCP
connections, the greater the inaccuracy is. Not all iSCSI TCP connections
are monitored for aging at the same time. Sessions, whose associated TCP
connections are not being currently monitored, will show unchanged aging
time.
• Encryption (Ipsec) must not be applied on iSCSI traffic, otherwise a QoS
profile will not be assigned to iSCSI.
• iSCSI optimization does not work with IP fragmented frames.
Summary of Contents for POWERCONNECT 5524
Page 415: ...Dell PowerConnect 55xx Systems User Guide 415 ...
Page 728: ......