5.1 Library Sharing Difficultities

[heada]

Hi All,



I have several servers running 4.2.3.0 on AIX 4.3.3 all sharing a single 3494 with 9 drives. I am planning on upgrading to TSM 5.1.5, but I think I may have a problem. Not all the 3590 drives have the same rmtX device as on the 3494 library master.



LIB_MAS = /dev/rmt0 (SN 0011320)

LIB_CLI1 = /dev/rmt2 (SN 0011320)

LIB_CLI2 = /dev/rmt5 (SN 0011320)



What happens when I try to setup library sharing with different rmtX devices? Can it work? How does the library client know which rmt goes with which drive?



Thanks for the help.



-Aaron

 

[chad_small]

With library sharing you don't actually "partition" the library by selecting different drives to different servers. Library sharing was really meant to be used with all drive shareable to other servers. My understanding from Tivoli support was that is was recommended that all drives be defined to both TSM servers. The new PATH function in TSM 5.1 makes this easier and harder at times. It' makes it easier by allowing you to manage multiple paths to a drive like NAS, Library Sharing, and Lan Free. The bad thing is now if one of the two (PATHS or DRIVES ..... since every DRIVE has at least one PATH associated with it) then that drive is offline. The only time this does not hold true is if the PATH is not one defined by the managing TSM server. The 3494 is shareable in a partitionable way that goes beyond TSM. So decide how you want to "share" the library. There are definite benefits in sharing it with all drive available to either server. Remember you can limit the number of drives a device class is allowed to use at once thereby making sure one or the other is not commandeering all drives at one time.



Chad Small

TSM Certified Consultant

IBM Global Services

[email protected]

 

[heada]

I don't think I made myself clear. I have 3 TSM servers, one as a library master and 2 library clients. I have 1 3494 tape library with 9 3590E drives. All TSM servers can see all the drives, but not as the same /dev/rmt device. This is due to some of the servers having locally attached drives (8mm and SCSI based 3590s)



Since the library master controls all the paths under TSM 5.1, how does library sharing take into account different /dev/rmt devices? All 3 servers see the same drive, but not as the same device.



-Aaron

 

[chad_small]

Good question. I didn't have the rmt problem when setting up my solution, but I know with 5.1.5 no paths are define on the LIB CLIENTS so I wonder if you even use the rmt settings as they show on the CLIENT or not? I wonder how the LIB MANAGEr would relate the CLIENT DRIVES to what it sees? I would think you would have to use the rmt' as they show on the CLIENT and that when the LIB MANAGER checks that rmt on the LIB CLIENT it is able to make some link between it's device list and those of the client. It would be nice if Tivoli would keep their information up to date.



Chad Small

TSM Certified Consultant

IBM Global Services

[email protected]

 

[tzong]

I think TSM should be smart enough, but if you really concern about that, you can configure the tape drives manually to make sure all the drive names on different servers are the same.

 

[heada]

Let me try to explain what I have again. I'll use TSM pre5.1 examples because I know them better.



The Library master (server-a) has a 3494 library defined with sharing turned on. Within that library are (9) 3590E1A drives (3494DRV00-08) with /dev/rmtX(0-8) devices for each. Each TSM server can see and use each 3590 drive via it's /dev/rmt device



On my library clients (server-b, server-c, etc...) I have a shared library defined with server-a as the library master. I have those same (9) drives defined with the same names (3494DRV00-08) BUT with different /dev/rmtX ((1-9) and (4-12)) devices.



Here is how I understand how TSM shares a 3494. Please keep in mind, I am _NOT_ a TSM guru, I just play one at work server-b wants to mount a tape. It talks to the library master (server-a) and asks for a drive and for a tape to be mounted. Server-a responds saying, "you can have 3494DRV00 and I'll mount the tape for you" Server-b then takes control of 3494DRV00 and waits for the tape to be mounted and when it is, it uses it. Since the data flows directly from server-b to the drive, it MUST use it's (server-b's) /dev/rmtX device.



What I fear will happen, is under 5.1, if the paths are only definded based on server-a, server-a will respond with "use drive XXX" and server-b will attepmt to use that drive, but will never see the tape mount because drive XXX is a different device on server-b.



Hope this sheds some light on my dilemma.



-Aaron