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Occasional Contributor
Posts: 17
Registered: ‎01-07-2010

Failed: already exceeds Buffer credits allowed.

I have a brocade5000 switch which was recently upgraded to FOS6.2.2.b and added the switch to our existing fabric and once I start ISL and add any host connections , we getting the bunch of warnings "Port (ID: 0) QOS is disabled", Then I have started enabling the qos on all attached and empty ports to stop getting that message. Once I reach the port28 I am getting the following error and the output of portbuffershow as follows.

Questions are , why it exceeded the buffer credits ? what does it mean ? how to get more buffer credits ? if I start using port#28,29,30 , I will get the continuous QOS disabled warning messages. Appreciate your help and how I can overcome this problem ?


fcsw:admin> portcfgqos --enable 28
Failed: already exceeds Buffer credits allowed.

fcsw:admin> portbuffershow
User     Port     Lx           Max/Resv    Buffer Needed          Link   Remaining
Port     Type    Mode          Buffers     Usage  Buffers     Distance  Buffers
----     ----    ----          -------     ------ -------     --------- ----------
  0        E      -              34         34      34             2km
  1               -               8          0       -             -
  2        E      -              34         34      34             2km
  3        E      -              34         34      34             2km
  4               -              34          0       -             -
  5               -              34          0       -             -
  6               -              34          0       -             -
  7               -              34          0       -             -
  8               -              34          0       -             -
  9               -              34          0       -             -
10               -              34          0       -             -
11               -              34          0       -             -
12               -              34          0       -             -
13               -              34          0       -             -
14               -              34          0       -             -
15               -              34          0       -             -
16               -              34          0       -             -
17               -              34          0       -             -
18               -              34          0       -             -
19               -              34          0       -             -
20               -              34          0       -             -
21               -              34          0       -             -
22               -              34          0       -             -
23               -              34          0       -             -
24               -              34          0       -             -
25               -              34          0       -             -
26               -              34          0       -             -
27               -              34          0       -             -
28               -               8          0       -             -
29               -               8          0       -             -
30               -               8          0       -             -
31        E      -              34         34      34             2km       16

Thanks

Frequent Contributor
Posts: 140
Registered: ‎02-27-2008

Re: Failed: already exceeds Buffer credits allowed.

HI mtata

You'll need to obtain a license to get more buffer credits for those ports which require it. Normally this is required when you have a fabric which is extended.

You mentioned you added this switch to your Fabric is this in your same data-center or another location.

Cheers

David

Regular Contributor
Posts: 201
Registered: ‎11-24-2009

Re: Failed: already exceeds Buffer credits allowed.

Hi mtata,

I'm not too familiar with QoS internals, but the important part I can see from portBufferShow output is for every QoS-enabled port there are 34 buffers allocated, and the last line says there are only 16 buffers remaining:

31     E     -     34     34     34     2km     16

Thus when you try to enable QoS on the next port (#28) it can only allocate 8+16=24 buffers instead of 34. I believe this is the reason why it fails.

Note that you're running a 4G Condor-based platform which was not initially designed to support QoS.

Hope this helps,

Linar

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: Failed: already exceeds Buffer credits allowed.

The 5000 switch has only 744 free buffers per port group. QoS settings has eaten up all free buffers.

In the beginning of FOS6.2 some support partners recommended to disable QoS on 4 Gbit platforms if do not use it.

Andreas

Occasional Contributor
Posts: 17
Registered: ‎01-07-2010

Re: Failed: already exceeds Buffer credits allowed.

HI Andreas and all ,

Thanks for your input .

How do I overcome this ? those 3 ports will be  in QOS disabled state all the time. If so, i will be getting alerts continously once it attaches to a host.

I have other swiches in the environment , they all are enabled by default.If I ignore the QOS disabled warning message, does that harm anything to the connection  or the port will keep go offline/online due to that ?, is that must to have QOS enabled ?  Is that true that I need to buy a lisence to get extra buffer credits ? Can you point me to a documentation to read more about buffer credits ?

Occasional Contributor
Posts: 17
Registered: ‎01-07-2010

Re: Failed: already exceeds Buffer credits allowed.

just to add a point .

In that fabric ports on primary switch 4900 all ports are QOS enabled. 4024 blade switch all ports QOS disabled.

Regular Contributor
Posts: 201
Registered: ‎11-24-2009

Re: Failed: already exceeds Buffer credits allowed.

Hi mtata,

QoS is an advanced traffic engineering feature, and it's optional. If you haven't configured QoS, it makes little sense to just turn it on. Thus it's perfectly safe to leave QoS disabled on all ports.

Contrary to what has been stated before, in your scenario you don't need a license to get extra buffers. That license only applies to extended distance ISLs. It doesn't create new buffers. It simply allows you to allocate more buffers for a given E-Port. You won't be able to overcome physical limitation of 744 buffers in the pool. And, as you're configuring F-Ports (devices), not E-Ports (ISLs), applying Extended Fabric license won't help you at all.

Buffer-to-Buffer credits mechanism is covered in Brocade Certified Fabric Administrator training as well as in many Fibre Channel introductory books.

Hope this helps,

Linar

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