fence_scsi man page on YellowDog

Man page or keyword search:  
man Server   18644 pages
apropos Keyword Search (all sections)
Output format
YellowDog logo
[printable version]


fence_scsi(8)							 fence_scsi(8)

NAME
       fence_scsi - I/O fencing agent for SCSI persistent reservations

SYNOPSIS
       fence_scsi [OPTION]...

DESCRIPTION
       fence_scsi  is  an  I/O	fencing	 agent which can be used with the SCSI
       devices that support persistent reservations (SPC-2 or greater).

       SCSI persistent reservations work by having each node  in  the  cluster
       register	 with the SCSI device. Registration is done using a unique key
       (based on the node's IP address). Each node that will perform I/O oper‐
       ations  to  the	shared	storage must register with the device. This is
       done at system startup with the scsi_reserve init script.  This	script
       will  discover  all  clustered  volumes	as well as the underlying SCSI
       device(s). Device discovery is done via the lvs	command	 (see  lvs(8))
       and is subject to any filtering rules defined in the lvm.conf file.

       After  generating  the  node's unique key, the script will register the
       node with the SCSI device(s) that were discovered.  Once	 the  node  is
       registered,  the	 script	 will  attempt to create a reservation. Unlike
       registrations, of which there are multiple registrants  (one  for  each
       node in the cluster), there is only one reservation holder. If a reser‐
       vation does not already exist for a device, the script  will  create  a
       reservation using the node's unique key.

       It  is important to distinguish between registrations and reservations.
       As mentioned above, each node that will perform I/O operations  to  the
       SCSI  device  must register. As a result, there will be multiple regis‐
       trations for a given SCSI device. In contrast, there can	 only  be  one
       reservation  per	 SCSI device. It is not important which node holds the
       reservation. The reservation simply tells the  device  how  the	regis‐
       trants are allowed to access the device. For our purposes, the reserva‐
       tion type is "write exclusive, registrants only".  With	this  reserva‐
       tion type, only registered nodes will be able to write to the device.

       When  the  cluster must fence a node, it simply revokes a node's regis‐
       tration, or "unregisters" the node. This operation also uses the node's
       unique  key.  By	 deriving the unique key based on the errant node's IP
       address, the cluster can "unregister" the key. As a result, the	errant
       node will no longer be able to write to the SCSI device.

       Note that the node that holds the reservation for a device must also be
       registered with that device. When the situation arises where  the  node
       that  is	 being	fenced is also the reservation holder, the reservation
       must be moved. This is handled by using the "preempt-and-abort command"
       which  will transfer the reservation from the node that is being fenced
       to the node that is performing the fencing. This operation  will	 main‐
       tain the reservation while "unregistering" the node being fenced.

       At  system  shutdown, the scsi_reserve script will attempt to "unregis‐
       ter" the node from all devices. The exception is when the node  happens
       to  be  the  reservation holder. In this case, the script does nothing,
       due to the fact that there may be other nodes using the device and  the
       reservation must remain intact.

       fence_scsi  accepts  options on the command line as well as from stdin.
       fenced  sends  parameters  through  stdin  when	it  execs  the	agent.
       fence_scsi  can	be  run	 by itself with command line options.  This is
       useful for testing and for turning outlets on or off from scripts.

OPTIONS
       -n node
	      Name of the node to be fenced.

       -h     Print out a help	message	 describing  available	options,  then
	      exit.

       -s self
	      Name of the node that will perform the fencing operation.

       -v     Verbose output.

       -V     Print out a version message, then exit.

STDIN PARAMETERS
       agent = < param >
	      This   option  is	 used  by  fence_node(8)  and  is  ignored  by
	      fence_scsi.

       nodename = < hostname | ip >
	      Name of the node to be fenced.

       self = < nodename >
	      Name of the node that will perform the fencing operation.

       verbose = < param >
	      Verbose output.

SEE ALSO
       fence(8), fence_node(8), sg_persist(8), lvs(8), lvm.conf(5)

								 fence_scsi(8)
[top]

List of man pages available for YellowDog

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net