10-22-2011
Hmm, I wonder what happens if you try to read a few GB from a SAN-based file system built on 4 or 6 or maybe more parallel LUNs configured by someone who knows how to lay out storage, and attached with 8 gbps fiber?
Do you really think the VM manager in your kernel can keep up with data coming in that fast?
Guess what? It can't.
Heck, I've seen well-designed 2 gbps SANs with just a few LUNs overwhelm VM managers.
In other words, YES, there ARE reasons to memset() a chunk of RAM *before* you use it.
And that's not even addressing the default Linux method of allowing oversubscription of virtual mamory in the hope that it won't all be used. If reliability and deterministic behavoir are important to you, you don't rely on hope and things like the Linux OOM killer are crazy-bad.
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LEARN ABOUT DEBIAN
fcoeadm
FCOEADM(8) Open-FCoE Tools FCOEADM(8)
NAME
fcoeadm - The Open-FCoE Administration Tool
SYNOPSIS
fcoeadm -c|--create ethX
fcoeadm -d|--destroy ethX
fcoeadm -r|--reset ethX
fcoeadm -i|--interface [ethX]
fcoeadm -S|--Scan [ethX]
fcoeadm -t|--target [ethX]
fcoeadm -l|--lun [ethX]
fcoeadm -s|--stats ethX [interval]
fcoeadm -h|--help
fcoeadm -v|--version
DESCRIPTION
The fcoeadm utility is the Fibre Channel over Ethernet (FCoE) management tool for the Open-FCoE project. fcoeadm may be used to create,
destroy, and reset an FCoE instance on a given network interface. For these operations fcoeadm sends a command to a running fcoemon
process, via a socket interface. fcoemon will then perform the requested operation.
fcoeadm also provides options to query information about FCoE instances, including interface information, target information, LUN
information, and port statistics. For much of this information, fcoeadm relies on the libhbalinux implementation of the HBA API.
OPTIONS
-c, --create ethX
Creates an FCoE instance based on the specified network interface. Note that if there is not an fcoemon configuration file for the
interface (/etc/fcoe/cfg-ethX, see fcoemon), then the created FCoE instance will not require DCB.
-d, --destroy ethX
Destroys the FCoE instance on the specified network interface. This will not destroy FCoE instances created by fipvlan.
-r, --reset ethX
Resets the FCoE instance on the specified network interface. This will not reset FCoE instances created by fipvlan.
-i, --interface [ethX]
Show information about the FCoE instance on the specified network interface, or all FCoE instances if no network interface is
specified.
-S, --Scan ethX
Rescan for new targets and LUNs on the provided instance. This command will not rescan any NPIV instances created on the same port.
This will not rescan any FCoE instance created by fipvlan.
-t, --target [ethX]
Show information about the discovered targets associated with the FCoE instance on the specified network interface. If no network
interface is specified, information about discovered targets from all FCoE instances will be shown.
-l, --lun [ethX]
Show detailed information about the discovered SCSI LUNs associated with the FCoE instance on the specified network interface. If no
network interface is specified, information about SCSI LUNs from all FCoE instances will be shown.
-s, --stats ethX [interval]
Show the statistics (including FC4 statistics) of the FCoE interface on the specified network interface. The information will be
display in one line on the screen per given time interval. interval should be specified in whole integers greater than 0. It specifies
the time interval in the unit of seconds. If interval is not specified, the default interval is one second.
-h, --help
Displays the usage message of the fcoeadm command.
-v, --version
Displays the version of the fcoeadm command.
EXAMPLES
Creates an FCoE instance on eth2.101
fcoeadm -c eth2.101
Destroys the FCoE instance on eth2.101
fcoeadm -d eth2.101
Resets the FCoE instance on eth2.101
fcoeadm -r eth2.101
Show the information of all the adapters and their ports having FCoE instances created
fcoeadm -i
Show the information of all FCoE instances on interface eth3.
fcoeadm -i eth3
Show the information of all the discovered targets from all the ports having FCoE instances created (they may be on different adapter
cards). A brief listing of discovered LUNs are listed after the target they are associated with, if any
fcoeadm -t
Show the information of all the discovered targets from a given port (eth3) having FCoE instance created. A brief listing of discovered
LUNs are listed after each target they are associated with, if any
fcoeadm -t eth3
Show the detailed information of all the LUNs discovered on all FCoE connections
fcoeadm -l
Show the detailed information of all the LUNs associated with a specific interface
fcoeadm -l eth3.101
Show the statistics information of a specific port eth3 having FCoE instances created. The statistics are displayed one line per time
interval. The default interval is one second if an interval is not specified
fcoeadm -s eth3
fcoeadm -s eth3 3
SEE ALSO
fcoemon(8)
SUPPORT
fcoeadm is part of the fcoe-utils package, maintained through the Open-FCoE project. Resources for both developers and users can be found
at the Open-FCoE website http://open-fcoe.org/
Open-FCoE 10/18/2011 FCOEADM(8)