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Full Discussion: Path missing???
Operating Systems AIX Path missing??? Post 302883449 by bakunin on Tuesday 14th of January 2014 08:54:43 AM
Old 01-14-2014
Quote:
Originally Posted by Thala
but why its getting 4paths for an Dual port adapter?
It has nothing to do with how many ports one adapter has. A "path" is just a way of looking at one disk. The short answer is, a "path" is a certain connection from the system to the disk, using a specific way.

Here is the long version: consider the following setup. You have one FC-Adapter (two ports, FCa, FCb), which is connected to two FC-switches (SWa, SWb), which both connect to a storage system. The switches are themselves connected via a crossover-link. You create a single disk on this storage system. This disk will be seen over different paths: FCa-SWa-Disk, FCa-SWa-SWb-Disk, FCb-SWb-Disk, FCb-SWb-SWa-Disk. AIX will therefore create 4 different hdisk-devices when you run cfgmgr.

Now, this is not very comfortable, especially when you create several disks. Each disk will be seen via 4 paths (if you have a fabric more complex than the one i sketched above you might have even more paths) and soon you will have trouble to remember that hdisk137 is in fact hdisk49 and also hdisk87 and hdisk3.

This is where MPIO comes into play: it takes all the hdisk-devices which represent in fact one and only one disk (its like taking a picture of a building from several angles - regardless of how many pictures you take it is always the same one building) and builds a "super-device" above them. You can use this super-device to build VGs, LVs and all other sorts of things you use normally disks for. The MPIO (Multipath-I/O) driver will take care about the relationship of the different hdisk devices and do the bookkeeping for you (and the OS as well).

And there is an additional advantage to it: suppose Switch A in the above picture would fail. Two of the four hdisks (the two paths involving SWa) would be inaccessible, because these pathes would not be usable, but the super-device still works, because it uses ALL paths and if two fail there are still two more to use. In fact this is the main reason one builds such complex fabrics with parallel FC-switches, crossover-links and the like.

I hope this helps.

bakunin
 

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LEARN ABOUT SUNOS

smartcard

smartcard(5)						Standards, Environments, and Macros					      smartcard(5)

NAME

       smartcard - overview of smart card features on Solaris

DESCRIPTION

       The  smart  card  framework provides a mechanism to abstract the details of interacting with smart cards and smart cardreaders (called card
       terminals). The framework is based on the OpenCard Framework V1.1 (OCF) with Sun extensions to allow OCF to operate in a  multi-user  envi-
       ronment.   The  core OCF software protocol stack is implemented as a system service daemon. This implementation allows smart cards and card
       terminals to be shared cooperatively among many different clients on the system while providing access control to the smart card  and  card
       terminal resources on a per-UID basis.

       An  event dispatcher is provided to inform clients of events occuring on the card and at the card terminal, such as card insertion and card
       removal.

       A high-level authentication mechanism is provided to allow clients to perform smart card-based authentications without requiring  knowledge
       of specific card or reader authentication features.

       A  set  of applet administration tools is provided for JavaCards that support downloading Java applets (although applet build tools are not
       provided).

       Administration of the smart card framework is provided with the smartcard(1M) command line administration utility and  the  smartcardguiad-
       min(1) GUI administration tool.

       Support the following card terminal is provided:

	 o  Dallas iButton Serial Reader (see ocf_ibutton(7D))

       Additional card terminals can be supported by implementing smart card terminal interfaces in a shared library.

       Support for several smart cards is provided:

	 o  Schlumberger Cyberflex Access JavaCard

	 o  Schlumberger MicroPayflex

	 o  Dallas Semiconductor Java iButton JavaCard

       Each  of  the  supported  cards	has  a complete set of OCF card services that implement the necessary functionality for authentication and
       secure storage of data. For the two supported JavaCards, an authentication and secure data storage applet is provided that  can	be  loaded
       into these cards with the supplied applet administration tools. See smartcard(1M).

       A PAM smart card module is provided to allow PAM clients to use smart card-based authentication. See pam_smartcard(5)

       CDE  is	able  to use the PAM smart card module for dtlogin and dtsession authentication. CDE also uses the smart card framework event dis-
       patcher to listen for events on the card terminal and provide corresponding visual feedback to the user.

SEE ALSO

       ocfserv(1M), smartcard(1M), libsmartcard(3LIB), pam_start(3PAM), pam_smartcard(5), ocf_ibutton(7D), scmi2c(7D)

SunOS 5.10							    16 Oct 2002 						      smartcard(5)
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