Migrating VAX to Integrity

[Petran Bisschops]

Dear all,

We are currently looking into upgrading/migrating from VAX hardware running VMS 6.2 to Integrity, probably RX2620 under VMS 8

I have a few questions where I hope you would share your experience with me:

a) We want to use a raid-5 hardware configuration. According the spec, this is shown to VMS as one physical device meaning we cannot configure/partition the device to make VMS believe we have multiple disk drives. Some of our applications require multiple disk devices.
Is there any solution for this?
I found out of the possibility to use the "logical disk utility" to generate more logical disk devices implemented as VMS container files. Is there anybody who can share some expiriences - reliability, perfomance etc.

b) we have to migrate all our Fortran based applications to this platform as well. Are there any issues to concider. Is this simular to migrating to Alpha?

c) Any other issues about itanium?

Your comments are as always greatly appriciated.

Petran.

[Volker Halle]

Petran,

there is a whitepaper for OpenVMS VAX to Integrity migrations:

http://h71000.www7.hp.com/news/vax_to_integrity.html

a) if you cannot find a Raid-5 controller, which makes multiple disks available to OpenVMS I64, you could use

- concealed devices (using logicals), if your application allows this
- use LDDRIVER to create LDAx: devices mapped to container files, see:

http://h71000.www7.hp.com/openvms/journal/v6/disk_partitioning_with_lddriver.html

b) migrating FORTRAN applications should be very easy. Re-compile and re-link.

c) access to un-aligned data could cause performance problems (more than on Alpha).

Volker.

[Volker Halle]

Petran,

what RAID 5 contoller do you have in mind ? Would it not support multiple logical drives ?

Volker.

[Petran Bisschops]

Volker,

Thanks for your reply.

The raid 5 controler we are opting for is of type A7173A - HP Dual Channel Ultra320 SCSI -5.

According the sales rep:
1) it can only be configured as RAID5
2) it is hot pluggable
3) The raid5 is shown as one disk device in VMS.

Thanks,

Petran

[Vladimir Fabecic]

Hello
Long time ago I had to migrate some applications from vax to alpha. Also had to have "multiple disk drives", but had just two raid disks (one RAID0 and one RAID5). I fixed that problem using concealed devices (using logicals). It is still working.
Something like:
DEFINE/TRANS=(CONC,TERM) disk1 dra1:[disk1...]
Not sure if it is correct sintax.

[Petran Bisschops]

Hello,

I did concider concealed devices but that won't work in all cases because I found DCL F$DEVICE calls and coresponding system service calls in the Fortran code - they won't return concealed devices.

Petran.

[Robert Gezelter]

Petran,

My first general recommendations are to:
- establish a set of qualification procedures that establish that the migrated (or new version) of the code functions at an acceptable level.
- secondly, I would recommend checking the FORTRAN sources for issues/incompatibilities BEFORE working on the IA64 platform.

The reasoning behind the above is straightforward: in the migration process, you will need to re-qualify the application more than once. An automated (or at least a scripted) process is more likely to give the assurance that your application is working than is an informal one.

There are also three sets of issues that you may encounter when moving the code: 64 bit issues, IEEE floating point issues, and IA64 specific issues.

Of those three, the IEEE Float issues are relevant if you have code that is VERY VERY floating point dependant. For example, if your application is a fluid dynamics simulation or other scientific application. These are not difficult to resolve, but I have seen cases where scientific/engineering codes depended on the details of the floating point format.

If your code is 100% classic FORTRAN, you should not encounter any 64 bit problems. I would also not expect IA64-specific problems.

A summary of the major issues can be found in my presentation on "The Third Porting", which was most recently presented for the Edmonton, Alberta (Canada) LUG in May 1995 (see
http://www.rlgsc.com/encompass-canada/edmonton/2005-05/OpenVMSonIntegrity.html for a copy of the slides).

As to the disk question, I have encountered the "multiple disk requirement" many times. The use of concealed logical names, and the OpenVMS logical name facility allows you to create a reasonable facsimile of a multiple disk environment, at least good enough in general for normal FORTRAN applications. As a first approximation, there is probably no need to bother with Logical Disks. I have written a series of columns on the the use of Logical Names (they can be accessed through my publications page at http://www.rlgsc.com/publications.html ).

I hope that the above is helpful.

- Bob Gezelter, http://www.rlgsc.com

[Robert Gezelter]

Petran,

I was writing my posting when you made your most recent posting about "F$DEVICE and corresponding other system service calls".

These may or may not be a problem, depending on what the information is used for.

Without looking at the code, it is hard (and for that matter, reckless) to speculate on what the application is doing with that type of information about a disk drive. It was not uncommon in days long past for applications to check the amount of free space on the drive and other details, in an attempt to optimize their operation. Hardware resources have long eclipsed this need (the resources available on a rx2600-class system dwarf even the larger members of the VAX family).

I would recommend a careful look at what the "F$DEVICE and corresponding system services" are precisely doing and how that information is used. The surface appearance of your application may be leading you into some unneeded configuration choices.

- Bob Gezelter, http://www.rlgsc.com

[Petran Bisschops]

Robert,

Thanks for your reply.

I will have a closer look at the code and see what it does.

One of the goals of my posting was also to find out about possible options so I can decide later on whats best (read: most cost effective?!)in our situation.

To all:

I would still appreciate some comments/experiences about the "logical disk utility"

Petran.

[Volker Halle]

Petran,

LDDRIVER is supported with OpenVMS I64, e.g. it's being used in @SYS$MANAGER:CDRECORD to create the image of the CD to be burned.

You can create container files and present them to OpenVMS as LD devices (like disks). You can then INIT and MOUNT those disks copy your files to those disks.

Also check the Smart Array adapters (A9890A and A9891A), which should be supported very soon on OpenVMS I64 V8.2-1, they may also allow multiple logical drives to be configured.

Volker.