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internal table on fiber drives?

Stumpr2
Level 6
I heard a strange comment while investigating Robert Misners thread
http://forums.veritas.com/discussions/thread.jspa?threadID=72550&tstart=0

Has anyone heard about a table of wwn/addresses located inside of a 9940B or similiar fiber tape drives? I heard a rumor but cannot find any documentation that said,.

The tape drive has a table of addresses that it will allow read/write access to the tape drive. There is only 16 slots available for these entries. This means that in order for a 17th media server to access this drive that it must wait for one of the existing 16 to drop out of the table. This is suppose to be the explaination as to why tape drives seem to disappear or become no longer functional to a media server.

I've heard stranger things but I wanted to see if this is an urban myth or if someone can supply me with documentation about this.
7 REPLIES 7

Dennis_Strom
Level 6
I know with Solaris if you do not add
forceload: drv/st
forceload: drv/sg
to the /etc/system file if the os has to many filesystem, cdrom, tapes ect.. loaded it will unload a tape drive that is not using. When the tape drive is called it will unload something else. This can slow things down. That is why it is recommended to put the forceload statement in the /etc/system file. This usually only happens during the day when the drives are not used so it slows down the startup of backups. usually when everything kicks off the drives are busy enought they do not get unloaded. I suppose it is possible with enough drives/robots being used it could happen, to a drive, in between jobs.
So I think this is controled by the OS not the drives. I know on Solaris/unix does this so that the OS can optimize resources. Did not know Windows did it.

Stumpr2
Level 6
Dennis,
That is a good point and readers should be advised to heed Dennis' input.

However, I am asking specific to the tape drive itself. Regardless of OS using the tape drive. I always thought that a tape drive is just suppose to be a dumb resource. This myth suggests that it keeps some intellegence as to what fiber nodes have accessed it and are allowed to continue to access it. Also, that it is limited to 16 fiber nodes. strange.....but is it true? and if it is, does any documentation exist?

Rakesh_Khandelw
Level 6
For latest Fiber tape drives there isn't any restriction on number of hosts can be attached (unless your SAN zoning is restricitng you to have more than x number of hosts).

This is something I found related to 9940B but not providing any information on why? Could be the POO for the rumor..... It is on StorageTek Website

HSC - What is the Maximum Number of Hosts that can be Defined to the CDS

The maximum number of hosts that can be defined to the CDS is 16. To provide library access for additional hosts, use one of the following methods:

* MVS/CSC and LibraryStation
* SMC and HTTP server (NCS 6.0 and higher)

https://extranet.stortek.com/primus/esupport/consumer/esupport.asp?number=4&isExternal=0&nShowFacts=&nShowCause=&nShowChange=&nShowAddInfo=&activepage=statement.asp&bForceMatch=False&strCurrentSymptom=hosts&searchtype=normalselected=solutionlistselected=solutionlist&searchclass=&bnewsession=false&selecttype=environment

Dennis_Strom
Level 6
access to the site requires username and password.

Stumpr2
Level 6
Rakesh
OK, I will mark this as a myth that cannot be substantiated. Sounds like someone had a clue but no facts! Thanks for the link. I had forgotten this resource. I had to search to find my loginID/password.

Dennis Erik,
Thank you for the extra effort you went to to try to find the documentation.

regards,
BS

Dennis_Strom
Level 6
No problem. I really wanted to know that one. So what does the link with the user name and password say?

This is by far the best Netbackup Forum in my not so humble opinion.

Stumpr2
Level 6
get your own loginID/password at
http://support.storagetek.com/globalnavigation/support/generalpublic/default.htm

BTW: you got mail!