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rschwabFlag for United States of America

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vmware san and fiber channel monitoring

Hello all
My question is that i have a client running a foxpro database in dbf format.   They are acessing this data via network share.  It is virtual server utilizing vmware the server image and all the dat data resides on SAN, acessed via fiber channel.
the problem is the application is dragging and access time isn't what it should be.  My feelings are that a dbf style data base that needs a client on workstation to perform the processiing is taxing the SAN with just way to many read, right and data transfers to the client.  This coupled with their entire infrastructure servers (that are virtualized) could be causing some type of issue.
the performance monitors show no excessive utilization in processing, disk activity nic or memory.
I guess i'm wondering can the fiber channel bus  be saturated while the disks show low utilization in perfomance monitor?  And can this be viewed from a vmware management console
Or am i reaching hear?    I look forward to any and responses  
 Thank you all for your time and input
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Pavel Celba
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Are you looking at local workstation performance monitor or at the server values?

I would guess the fiber channel is not the problem but some server diagnostic software will tell more.

Following points are focussed on the application itself but without its detail knowledge it will be difficult to help.

The application speed depends mainly on its architecture and the way of data access. As a rough estimation if your application is slow or not you can test the sequential data read/write speed by copying some file between SAN and your local workstation.

The FoxPro application:
1) Should be installed on local workstation
2) Place all temporary files on the local workstation
3) Should use indexes to optimize data access performance
4) Should not open/close shared files periodically
5) Should lock data records for the shortest possible period of time
6) Should not lock whole files in multiuser environment
etc.

How many concurent users are working with same data? You could also measure some multiuser data access (for different number of users) versus exclusive data access. (Exclusive access is much faster always but not 10 times - it could point to bad network/system settings.)
VFP being a file server database, will utilize the network more that a client server database. You will have to check the indexes and optimize the database.
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Olaf Doschke
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Olaf, do you have some link or source of the "locking behind the end of file" concept? It sounds like a nonsense to me because if you lock something else than the physical record itself other (non-fox) applications could lock the same record physically and write to it...

I could imagine the lock of one byte with offset 2G minus record number as a quick test of record availability but after such test the physical record locking must follow (and only this physical lock allows the only one FoxPro instance to write data into the record).

I agree the locks after the EOF could cause some system slow downs but I have no data to confirm it.

This concept of VFP's locking is documented, for example here: http://fox.wikis.com/wc.dll?Wiki~RLOCK
The wiki also suggests to use FileMon to see what happens and explains why this is done this way, to still allow reading the locked record.

Bye, Olaf.
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Guys thank you so much for your comments,   The fox pro app i'm refering to is an app that been sold to  around 200 customer it's been in service for about 8 years  each customer implement this app in their own environment.  on average each customer has anywhere from 20 to 80 users accessing it concurrently.   so the app is rather stable.   It just this environment that seem s to be dragging it down.

My thought is that the disk utilization within the vm environment is low but the fiber bus is what's saturated.
there is the possibility of network issues as well.  my other thought was to put the data on a physical box and move the server to the physical location of the bulk users.
Thanks Olaf, I have to confirm, you were right, VFP locks bytes from "2G down" only... And the lock means reserved access for one process. I supposed the file lock prevents write access on OS level. I don't know why I missed this info earlier.

Interesting behaviour is when you issue FLOCK():  VFP decided to lock 85 MB block somewhere around 2GB offset in my less than 1 KB dbf.

This simply means we can write routines which will ignore VFP file and record locking (maybe such routine already exists and its name is Clipper :-)

Still learning.
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depends on how many users are accessing that share, but it could be a matter of looking at how your servers are accessing those LUNs.  if your servers have two channel HBAs, it might be worth looking at the preferred paths for each, and trying to balance them out to spread the load.  what SAN do you have?  is there not diagnostic software for it?  when we had performance issues with a psql database we submitted the service log to IBM and they had some minor tweaks for us to try, although in the end it was a database problem, we were still able to fine tune our setup a bit with their assistance.
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I guess i'll find out tomorrow,   There're placeing the data on a dell 2950 stand alone.  it's easy test so well see.  Stephen    it's a  Dell/EMC array CX3-20.  It's not my box but i'll get a better look at it tommorrow.  it wasn't clear if th were giving me performance info off the san or the virtual image
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Thank you guys the combination of all you knowledge help me to eliminate the vmware san issue at this point.  After getting both both termserver and production data off the the San the performance remained the same.   It seems a Dell 5424 power connect switch maybe the culprit.  Further actions are underway to segment the device from the switch.  as well as Dell providing software upgrades  "hhhhhhhhmmmmm wonder why that is "    Thanks again for all your help and confirming some of my actions