[Info-vax] Replacement of SCSI tape drives and loaders

[Kari Uusimäki]

On 21.1.2010 21:11, Syltrem wrote:
> Hi
>
> I have 2 Alpha servers, each with SCSI connected tape drive(s)
>
> I want to move the drives from one server to another, and install a new one.
>
> QUESTION: Can I do this live ?
>
> My experience (on VAX) is that I can disconnect / reconnect the same drive
> on the VAX and it will not notice, as long as I DO NOT attempt to use the
> drive (do a MOUNT or INIT etc) on it while it is disconnected. Doing so
> would crash the VAX.
>
> On Alpha it may be different, the HP tech says it should work just fine. I
> just want to double check here.
>
> Details :
> On the AS4100 I have a standalone DLT4 drive MKB600
> On the ES40 I have a TL891 mini-library with 2 DLT4 drives MKA400 and MKA500
>
> I want to disconnect the standalone DLT4 drive from the AS4100 and connect
> the TL891 and its drives in replacement.
> On the ES40 in replacement of the TL891 I want to install a new LTO4 drive.
>
> So... the AS4100 will get 2 drives instead of 1, and the ES40 will loose one
> drive and the replacement one will be of a different model.
>
> QUESTIONS:
> - Should I care about the new drives SCSI addresses ?
> - VMS on the ES40 will continue to see the old device (let's say MKA500 if
> the new one replaces MKA400) which is disconnected. If by mistake some
> process tries to access it, will it cause VMS to crash ?
> - If I keep the same SCSI address, does it matter if suddenly (as far as VMS
> sees it) the drive model is different ?
> - The speed of the drive is also different. Without a reboot will VMS make
> the best use of the new unit (the speed of the devices on the bus have
> changed) ?
>
> This is NOT something I've done before so I just don't know.
> My guess is that I should shutdown the servers to do this, but I'd rather
> not if it's not required (24/365 shop)
>
> Merci
> Syltrem
>
>

Yes, you can do it live, when you keep in mind some basic, but very 
important things.
First, do not connect or disconnect peripherals when they are switched 
on. Do always switch them off before making any changes. Preferably 
disconnect the power cord also.
Second, you have to mind about the SCSI addresses to be sure you don't 
have two devices with same address. That will really produce 
unpredictable behaviour.
Third, it is good to update the I/O structures when you have 
disconnected the old peripherals and connected the new ones, but before 
you switch the new ones on, by issuing the command
$ MC SYSMAN IO AUTO /LOG
The old peripherals should turn from online to offline.
Then switch the new ones on and do once more
$ MC SYSMAN IO AUTO /LOG
Now the new peripherals should appear in the device list.
The speed of the drive should be correct at once if your version of 
OpenVMS recognizes it correctly (i.e. the VMS version is new enough).
There might be a faint possibility that someone would have fiddled with 
the SCSI adapter settings which would cause the bus not to work with 
full speed. But you'll find that out when you test the drive.
One thing you probably need to do is to generate the robotics control 
device on the machine where you connect the tape library.
You can do that live also. You need th know the bus ID and the SCSI ID 
of the robotics controller. Lets say it is SCSI ID 1 on the third SCSI 
bus (C)
$ MC SYSMAN IO CONNECT GKC100: /NOADAPTER /DRIVER=SYS$GKDRIVER
Then you should have a device named GKC100: which is the one you need to 
access the robotics. Most probably you need to update your backup 
application or procedure to include the robotics device name.
If you have the MRU utility installed, you can test the robotics 
functions manually
(e.g. $ robot show robot)


Good luck!

Kari