OpenVMS 8.3 SSH performance

Rikki hinn Ogurlegi — Tue, 08 Jan 2013 17:48:40 GMT

Hello all,

I have a two node VMS cluster running OpenVMS 8.3. These two nodes run a X11 graphical program many people here need to access. Clients are mostly using Xming (or hummingbird) on Windows.

Traditionally people have logged in via telnet, set their DISPLAY variable and then run the program. This is however quite fragile as IP addresses can change and the telnet service on the VMS boxes seems to stop working rather frequently.

So I started experimenting with using SSH and SSH X forwarding to handle this for me, and as an added bonus get rid of plain text passwords and other data flowing thru the LAN here.

Both Xming and Hummingbird know how to use either putty.exe or plink.exe so the setup and config was easy. However once the app is running I see almost a 10 fold increase in latency when using the program. Flipping pages in the app was quite responsive when X was connecting directly but becomes very sluggish via SSH.

I tested logging in to a Linux machine that is in the same server room as the VMS cluster with putty and X11 forwarding and running apps on them and they did not show any slowness over SSH, compared to direct X11 connections.

So I need to figure out why SSH connections to OpenVMS 8.3 are so slow. It does remind me of a very old problem I had with HP-UX back in the day when HP-UX did not have a decent /dev/random device and SSH was starved for decent entropy for encryption purposes, but I have no way to know if this is the case on VMS as I'm really not that good with VMS.

Any help would be appreciated.

Thanks in advance,

Richard.

Re: OpenVMS 8.3 SSH performance

Steven Schweda — Tue, 08 Jan 2013 22:24:08 GMT

Re: OpenVMS 8.3 SSH performance

Rikki hinn Ogurlegi — Wed, 09 Jan 2013 13:27:19 GMT

>> I have a two node VMS cluster running OpenVMS 8.3. [...]
>
> Not much meat on that bone. About what kind of hardware are we
> talking? AlphaStation 200/100? Some fancy multi-GHz-CPU server?
> Memory? Quotas?

ELAS_SYS:ISLANDV2.0==>sh cpu

System: ELAS05, AlphaServer DS15A

CPU ownership sets:

Active 0

Configure 0

CPU state sets:

Potential 0

Autostart 0

Powered Down None

Not Present None

Hard Excluded None

Failover None

ELAS_SYS:ISLANDV2.0==>sh mem

System Memory Resources on 9-JAN-2013 11:23:03.97

Physical Memory Usage (pages): Total Free In Use Modified

Main Memory (512.00MB) 65536 16090 48610 836

Extended File Cache (Time of last reset: 15-JUL-2012 05:45:12.01)

Allocated (MBytes) 111.62 Maximum size (MBytes) 256.00

Free (MBytes) 0.00 Minimum size (MBytes) 3.12

In use (MBytes) 111.62 Percentage Read I/Os 79%

Read hit rate 91% Write hit rate 0%

Read I/O count 4072288894 Write I/O count 1034334960

Read hit count 3741138370 Write hit count 0

Reads bypassing cache 75807 Writes bypassing cache 31882

Files cached open 490 Files cached closed 147

Vols in Full XFC mode 0 Vols in VIOC Compatible mode 3

Vols in No Caching mode 0 Vols in Perm. No Caching mode 0

Granularity Hint Regions (pages): Total Free In Use Released

Execlet code region 1024 0 980 44

Execlet data region 512 0 414 98

S0S1 Executive data region 680 0 680 0

S0S1 Resident image code region 2048 0 1213 835

Slot Usage (slots): Total Free Resident Swapped

Process Entry Slots 356 292 62 2

Balance Set Slots 354 292 60 2

Dynamic Memory Usage: Total Free In Use Largest

Nonpaged Dynamic Memory (MB) 15.45 10.26 5.18 0.15

Bus Addressable Memory (byt 0.00 0.00 0.00 0.00

Paged Dynamic Memory (MB) 3.62 2.05 1.57 2.03

Lock Manager Dyn Memory (MB) 2.57 1.11 1.45

Buffer Object Usage (pages): In Use Peak

32-bit System Space Windows (S0/S1) 2 34

64-bit System Space Windows (S2) 0 0

Physical pages locked by buffer objects 2 34

Memory Reservations (pages): Group Reserved In Use Type

Total (0 bytes reserved) 0 0

Swap File Usage (8KB pages): Index Free Size

DISK$VMS83R1:[SYS0.SYSEXE]SWAPFILE.SYS

1 2640 2768

Paging File Usage (8KB pages): Index Free Size

DISK$VMS83R1:[SYS0.SYSEXE]PAGEFILE.SYS

254 45980 66048

Total committed paging file usage: 46129

Of the physical pages in use, 6818 pages are permanently allocated to OpenVMS.

Not sure how to see if quotas are getting in the way of SSH processing.

>> [...] the telnet service on the VMS boxes seems to stop working rather
>> frequently.
>
> Not a very complete problem description.

It's the best I can do. I have'nt diagnosed that problem as I still feel that ssh is the way to go.

>> [...] very sluggish [...]
>
> What investigation have you done? Is the CPU (are all the CPUs)
> busy while this stuff is running? Memory? Page-fault rate? For a
> start:

Just basic things as I'm not that familiar with VMS. The X11 program we are running displays pages that contains multiple text fields and some graphs. The most telling of these tests is to simply open the program and quickly hit page down a few times. When using direct X connections the program flashes as many pages as the page down key was hit.

But when using X forwarding via ssh, the program just prints the first page and then the last. It may print a few pages inbetween if the page down key is pressed often enough.

It also takes longer to start and do most other operations.

>> [...] a Linux machine [...]
>
> The description of this hardware is no more useful than the earlier
> one of the VMS hardware. I would not be amazed if a modern,
> resource-rich x86 system were faster than some decade-old, resource-poor
> Alpha system. But, with my weak psychic powers, I know approximately
> nothing about your hardware (or the users' resource quotas, or anything
> else, really).

The machine is just a single cpu DL360 G5 box running RHEL6. Im pretty sure I did not describe my problem well enough but in my mind, running SSH should not be that much of a hassle for any machine. I've got 15 year old HP9000 L2000 machines with PA-RISC cpu's running HP-UX 11.23 who perform very well with SSH.

Re: OpenVMS 8.3 SSH performance

Steven Schweda — Wed, 09 Jan 2013 18:04:05 GMT

Re: OpenVMS 8.3 SSH performance

abrsvc — Wed, 09 Jan 2013 18:10:35 GMT

Slot Usage (slots): Total Free Resident Swapped
Process Entry Slots 356 292 62 2
Balance Set Slots 354 292 60 2

=============

The portion of the SHO MEM above indicates to me that you are running a bit short on memory. As indicated by Steven, get more memory for this system. That should make a tremendous difference overall.

Dan

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