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

[Bob Koehler]

In article <ZF16n.101149$dl4.56657 at en-nntp-03.dc1.easynews.com>, "Syltrem" <syltremzulu at videotron.ca> writes:
> 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.
> 

   I think the most important thing is to make sure the SCSI bus is
   absolutely quiet when your doing this.

> QUESTIONS:
> - Should I care about the new drives SCSI addresses ?

   Yes.  You'll need an address that is not already in use.

> - 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 ?

   I would not be the least surprised.  You off into an unsupported
   hardware configuration here.
   
> - If I keep the same SCSI address, does it matter if suddenly (as far as VMS 
> sees it) the drive model is different ?

   Very good chance that that won't work.  Try it on a non-operational
   system first, and then make sure you're not betting the business.

> - 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) ?

   You should be OK, if you don't use the same SCSI address.  If you do
   and VMS can talk to the drive, then it will assume that it's the old
   drive.
 
   If at all possible, I would schedule a few minutes of power-off time
   in oder to do this.  If you have a high availability cluster setup,
   you should be able to keep your applications available.