Discussion:
z/OS DFS SMB Performance
(too old to reply)
Smith, Sean M
2006-03-30 16:40:01 UTC
Permalink
Problem:

When connecting to work over VPN, SMB performance leaves a lot to be
desired. Where a 200k file in the office loads in 5-9 seconds, over VPN
it takes 50-60 seconds. It does not appear to be a server problem or a
bandwidth problem. I tried the same file directly pulling it from an
HFS and I got it loaded in 6 seconds from home. I then setup a file
server on a z/OS box to see if it would perform better. It did not.
Talking to local VPN expert, he basically said that SMB is "chatty" and
that we will see some improvement with Windows Vista.





Reading the DFS manual for SMB, there are several notes about
performance one of which states that HEAPPOOLS(ON) provides a
significant improvement. What they don't say is what the heap pool
sizes and percentages should be for SMB. I am overriding the HEAPPOOLS
in the JCL so these will not be system wide. I tried HEAPPOOLS(ON) and
did see a good improvement.



Any help would be appreciated.



Sean Smith

Bank of America


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R.S.
2006-03-30 18:29:25 UTC
Permalink
Is the VPN terminated outside from z/OS ?
I mean:
[1]---encrypted-Inet--- [2] ---clearLAN--- [3]

1 - remote PC with VPN
2 - local VPN device
3 - mainframe

Is the above true ?
--
Radoslaw Skorupka
Lodz, Poland
Post by Smith, Sean M
When connecting to work over VPN, SMB performance leaves a lot to be
desired. Where a 200k file in the office loads in 5-9 seconds, over VPN
it takes 50-60 seconds. It does not appear to be a server problem or a
bandwidth problem. I tried the same file directly pulling it from an
HFS and I got it loaded in 6 seconds from home. I then setup a file
server on a z/OS box to see if it would perform better. It did not.
Talking to local VPN expert, he basically said that SMB is "chatty" and
that we will see some improvement with Windows Vista.
Reading the DFS manual for SMB, there are several notes about
performance one of which states that HEAPPOOLS(ON) provides a
significant improvement. What they don't say is what the heap pool
sizes and percentages should be for SMB. I am overriding the HEAPPOOLS
in the JCL so these will not be system wide. I tried HEAPPOOLS(ON) and
did see a good improvement.
Any help would be appreciated.
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Smith, Sean M
2006-03-30 20:07:23 UTC
Permalink
Yes I believe that is the case. We are not using z/OS for the VPN
service.

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-***@ibm-main.lst
Behalf Of R.S.
Sent: Thursday, March 30, 2006 10:29 AM
To: IBM-***@BAMA.UA.EDU
Subject: Re: z/OS DFS SMB Performance

Is the VPN terminated outside from z/OS ?
I mean:
[1]---encrypted-Inet--- [2] ---clearLAN--- [3]

1 - remote PC with VPN
2 - local VPN device
3 - mainframe

Is the above true ?
--
Radoslaw Skorupka
Lodz, Poland
Post by Smith, Sean M
When connecting to work over VPN, SMB performance leaves a lot to be
desired. Where a 200k file in the office loads in 5-9 seconds, over
VPN
Post by Smith, Sean M
it takes 50-60 seconds. It does not appear to be a server problem or
a
Post by Smith, Sean M
bandwidth problem. I tried the same file directly pulling it from an
HFS and I got it loaded in 6 seconds from home. I then setup a file
server on a z/OS box to see if it would perform better. It did not.
Talking to local VPN expert, he basically said that SMB is "chatty"
and
Post by Smith, Sean M
that we will see some improvement with Windows Vista.
Reading the DFS manual for SMB, there are several notes about
performance one of which states that HEAPPOOLS(ON) provides a
significant improvement. What they don't say is what the heap pool
sizes and percentages should be for SMB. I am overriding the
HEAPPOOLS
Post by Smith, Sean M
in the JCL so these will not be system wide. I tried HEAPPOOLS(ON)
and
Post by Smith, Sean M
did see a good improvement.
Any help would be appreciated.
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send email to ***@bama.ua.edu with the message: GET IBM-MAIN INFO
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R.S.
2006-03-31 08:02:24 UTC
Permalink
Post by Smith, Sean M
Yes I believe that is the case. We are not using z/OS for the VPN
service.
In that case you should notice similar speeds on same speed link, with
or without VPN.
I know your non-VPN connection is LAN connection, probably much faster
than VPN connection.
If possible try to connect via VPN locally and compare the speed with
direct connection.
Don't compare i.e ftp speed to SMB speed, SMB is not fast.

How can VPN influence SMB performance (my guesses):
1. Different (smaller) IP packets causing worse performance.
2. Additional data in packets causing overhead: you SMB transmit 100kB,
VPN transmit it as 130kB.
3. VPN devices are CPU-overloaded with encryption/decryption.
4. "VPN does not like SMB" <vbg> It Windows-like technology...
--
Radoslaw Skorupka
Lodz, Poland

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John S. Giltner, Jr.
2006-03-31 01:29:49 UTC
Permalink
From my experience SMB on any platform is slow. Think about it, a 200K
file loading in 5-9 seconds in the office. That is a transfer rate of
somewhere between 20 to 40 K a second. Now add the overhead of a VPN
and the latency and through put of something that is most likely much
less than the network between your PC and the mainframe at your work.

What is the slowest network connection in your office?
What is the speed of the network that your VPN is transversing?

What do you mean pulling it directly? FTP? FTP is much more efficient
that SMB.

SMB is real chatty. IIRC it does one ACK for every two data packets and
the ACK is not sent until the data packets are received. This is on top
of the TCP level ACK's.
Post by Smith, Sean M
When connecting to work over VPN, SMB performance leaves a lot to be
desired. Where a 200k file in the office loads in 5-9 seconds, over VPN
it takes 50-60 seconds. It does not appear to be a server problem or a
bandwidth problem. I tried the same file directly pulling it from an
HFS and I got it loaded in 6 seconds from home. I then setup a file
server on a z/OS box to see if it would perform better. It did not.
Talking to local VPN expert, he basically said that SMB is "chatty" and
that we will see some improvement with Windows Vista.
Reading the DFS manual for SMB, there are several notes about
performance one of which states that HEAPPOOLS(ON) provides a
significant improvement. What they don't say is what the heap pool
sizes and percentages should be for SMB. I am overriding the HEAPPOOLS
in the JCL so these will not be system wide. I tried HEAPPOOLS(ON) and
did see a good improvement.
Any help would be appreciated.
Sean Smith
Bank of America
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Bruno Sugliani
2006-03-31 04:37:44 UTC
Permalink
On Thu, 30 Mar 2006 20:29:15 -0500, John S. Giltner, Jr.
Post by John S. Giltner, Jr.
From my experience SMB on any platform is slow. Think about it, a 200K
file loading in 5-9 seconds in the office. That is a transfer rate of
somewhere between 20 to 40 K a second. Now add the overhead of a VPN
and the latency and through put of something that is most likely much
less than the network between your PC and the mainframe at your work.
What is the slowest network connection in your office?
What is the speed of the network that your VPN is transversing?
What do you mean pulling it directly? FTP? FTP is much more efficient
that SMB.
SMB is real chatty. IIRC it does one ACK for every two data packets and
the ACK is not sent until the data packets are received. This is on top
of the TCP level ACK's.
I had a presentation by cisco people about their VPN accelerator ,their AVS
( appl velocity system) their WAFS ( wan accelerator for file system) and
WAE ( wan accelerator engine) ,
Obviously WAFS has been invented for the exact problem you are facing .
The chat to open a document with word or excell over a network .
The number they showed me was like 1000 exchanges to open and close a file
and they were dividing this by 8 or 10 , by letting only the security
portion of the handshaking flow ( enqueue etc .. ) and by simulating a big
part of this handshaking on both ends to reduce the chatyness , and trying
to let flow the data only .
The improvement is just tremendous .
try to find out on google how this WAFS , WAE and cisco accelerator work
and it will give you some good insight in what John is describing exactly .
Bruno
Bruno(dot)sugliani(at)groupemornay(dot)asso(dot)fr

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