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Conference smurf::ase

Title:ase
Moderator:SMURF::GROSSO
Created:Thu Jul 29 1993
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2114
Total number of notes:7347

1933.0. "Root disks on shared bus" by MSDOA::mko-ras-port-12.mko.dec.com::KLOPEZ (Ay, Caramba!) Mon Mar 10 1997 20:12

Hello,

I shouldn't be asking this, I have already read note 1506, and 
understand the implications of having the operating system disk inside 
the shared bus. 

My problem is that our customer wants to use RAID 1 + WBC for the 
operating system disks and he wants to place the root disks on the 
HSZ40.

I have explained to him the problem he could have if he accidentally
mounts the system disk on the wrong server, but he wants me to find
out if there's a workarround to this. Is there a way to protect system 
disks when installed on the SCSI shared bus? He even suggested hidding
the mount command from the operating system in order to prevent an 
accident.
 
In some notes I have found there's no technical reason to use the disks 
on the shared bus, and in our case we are not planning to share them, 
we would only want to be sure we don't have additional problems besides
the security problem.

Thanks in advance for your help,

Katya
T.RTitleUserPersonal
Name		DateLines
1933.1some alternativesDOOSJE::HERTAFor something fulfilled this hour, loved, or enduredTue Mar 11 1997 04:1826
Re:.0
> Is there a way to protect system 
> disks when installed on the SCSI shared bus?  He even suggested hidding
> the mount command from the operating system in order to prevent an 
> accident.

Nope.  As an example, when we want to test whether our shared devices are reachable
from all ASE members, we issue commands such as
  # dd if=/dev/rrza49c of=/dev/null
It'd be easy to replace /dev/null by a system disk device.

I heard of a customer who did set up his cluster with system disks on shared devices,
so, yes, technically it can be done.  But the customer had to sign a contract in
which was clearly stated that the configuration was an unsupported one, and that 
Digital could not be held responsible in case something went wrong.

> My problem is that our customer wants to use RAID 1 + WBC for the 
> operating system disks 
Supposing the customer has some sort of battery or UPS support for his system, you
could also implement it rather inexpensively using KZPSC-BA RAID controllers.
Software-wise, you could also use LSM to implement RAID 1.

I guess the real question is, why does the customer want to put his system disks in
the HSZ40?

Herta
1933.2$$$$MSDOA::mko-ras-port-17.mko.dec.com::KLOPEZAy, Caramba!Tue Mar 11 1997 10:3914
Thanks for your reply,

** I guess the real question is, why does the customer want to put 
** his system disk the HSZ40?

Well he doesn't want to buy new hardware, and the elements we are 
counting on are the HSZ40, the KZPDA (included with the AlphaServer) and
KZPAA's we are using for tape drives.

I recommended LSM for RAID 1, but they want WBC for their swap devices.

Thanks,

Katya
1933.3make a minimal cost/benefit analysisDOOSJE::HERTAFor something fulfilled this hour, loved, or enduredTue Mar 11 1997 11:507
Check the price for a KZPSC-AA, and compare to the cost of restoring the system 
disk just once (restoration of backup + production down-time).  Then ask the 
customer if he considers the risk is worth it or not.

Good luck.

Herta