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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

1962.0. "ASE and HSZx0 configuration issues" by GOYA::GALAN () Wed Mar 19 1997 18:47

    Hi everybody.
    I'd like to clarify two issues about DECsafe and HSZ*0 configuration.
    
    I didn't read anything against these, but I want to be completely sure
    they are supported. These issues are for a very important customer, and we
    don't want to add any dangerous or problematic configuration.
    
    >> First question.
    This is about if we can configure two (or even 3) dual HSZ50 pairs
    in the same shared bus. At this moment the customer has something like
    	KZPSA --- dual HSZ50 pair --- KZPSA
    
    in a DECsafe AS4100 cluster.
    And we want to do 
    
    KZPSA --- dual HSZ50 pair ---- dual HSZ50 pair --- KZPSA
    
    Even if the performance will not be great, what I want to know is:
    - is this supported?
    - is there any hardware problem, any ASE software problem, ... to do
    this configuration?
    - is this only a qualification issue?
    
    >> Second question.
    In the actual configuration 
    
    KZPSA -- dual HSZ50 pair --- KZPSA
              SW800 cabinet
    
    we have in the same shared SW800 cabinet, some volumes (RAID with
    HSZ50) under DECsafe control, ie, the two systems mount these volumes
    (and there is failover of them), and another volumes that only one of 
    the system manages. Of course there is not failover of the second
    volumes.  
    The system manager always mounts by hand this last volume in the system A, 
    and when this system fails, mounts by hand the same volume in the system B.
    So there is not problem with data corruption or things like that. 
    
    My question is:
    - is this supported? Can you have in the same shared SCSI bus with
    DECsafe some volumes mounted by the two systems (ASE services), and
    another as simple Advfs filesystems mounted only for one of the system
    at the same time?
    I mean I want to know if the fact to have some volumes (different
    disks, of course) in the SW800 not under the control of DECsafe can
    produce any problem to the cluster configuration.
    
    Thanks a lot,
    Ana Galan
    PreSales Technical Support  Ayr - Scotland
    E-mail: galan@ayo.mts.dec.com

T.R	Title	User	Personal Name	Date	Lines
1962.1	Why not using ASE ?	BACHUS::DEVOS	Manu Devos DEC/SI Brussels 856-7539	`Fri Mar 21 1997 12:05`	19
	Hi Ana, I am going to let somebody else answering the HSZ question. Concerning the use of a disk NOT managed by DECsafe on a shared SCSI bus, it is TECHNICALLY feasible and WORKING, but is also exposing this disk to data corruption by the other system. Decsafe is placing an hardware "reservation" bit on all the disks serviced by a DECsafe service attached to SYSTEM A such that system B receive an error status if it tries to access them. So the data are protected. It is NOT the case outside of DECsafe. By the way, if the customer has the DECsafe license, and if the disk is placed on the shared bus, why is he not creating an ASE disk service with that disk? He would only have to use asemgr to move his filesystem to the other system ! Regards, Manu.
1962.2	n*HSZ50 on one bus	NETRIX::"pelle@.zk3.dec.com"	Pelle Wahlstrom	`Fri Mar 21 1997 13:42`	21
	>> First question. >> This is about if we can configure two (or even 3) dual HSZ50 pairs >> on the same shared bus. >> KZPSA --- dual HSZ50 pair ---- dual HSZ50 pair --- KZPSA >> - is this supported? Don't know, >> - is there any hardware problem, any ASE software problem, ... to do >> this configuration? I don't see any HW or SW problems. Each HSZ50 controller dual pair would use up 2 scsi-ids on the bus and each KZPSA will use up 1 scsi -id. There are 8 scsi-ids available => You can have 3 dual HSZ50 pairs on one scsi bus. However, performance will be very bad, even with 2 pairs. But, if the customer wants access to a lot of data and doesn't access it very intensively, it seems OK. >> - is this only a qualification issue? Yes [Posted by WWW Notes gateway]
1962.3	Works but...	AUSSIE::MCNAMARA		`Fri Mar 21 1997 19:06`	32
	G'Day Ana, I guess like everythig it depends on "what the customer is trying to achieve" By connecting multiple HSZxx controllers onto the same SCSI bus they create a single point of failure which seems to compromise the case for DECsafe in the first place. A better solution would be to spread the HSZxx controllers over multiple shared bus connections and if data security is important use single HSZxx controllers and software mirror between the SCSI bus with LSM. The redundant controllers do not protect against a SCSI cable or terminator failure. (or some misguided human resource unit tampering with the wrong cable) But I guess if the customer has :- - No more available I/O slots to add another controller and wants to add lots more storage AND does not want to access this data at high speed. or - Does not have a problem with single points of failure in their high availability system. (In which case why fit redundant HSZxx controllers) It should work,however, I would advise against this option and as .1 suggests why not have the shared discs handled by ASE? the manual system is very prone to "User Error On Device" Regards Scott