Mainframe & FICON

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Occasional Contributor
Calgada
Posts: 5
Registered: ‎10-11-2012

GE Fifo overflow

Hi guys,

On one of our Brocade (switchType:     83.3) we have a GE port dedicated for FCIP replication for our IBM storwize (100km distant).

On this port we get regular GE FIFO overflow errors:

> portstatsshow ge0

ge_stat_tx_frms                  163267708285   GE transmitted frames

ge_stat_tx_octets             168983842881620   GE transmitted octets

ge_stat_tx_ucast_frms            163267485251   GE transmitted unicast frames

ge_stat_tx_mcast_frms                       0   GE transmitted multicast frames

ge_stat_tx_bcast_frms                  115734   GE transmitted broadcast frames

ge_stat_tx_vlan_frms                        0   GE transmitted vlan frames

ge_stat_tx_pause_frms                  107300   GE transmitted pause frames

ge_stat_rx_frms                  104557403739   GE received frames

ge_stat_rx_octets              21666295301492   GE received octets

ge_stat_rx_ucast_frms            104212900056   GE received unicast frames

ge_stat_rx_mcast_frms               162829338   GE received multicast frames

ge_stat_rx_bcast_frms               163326966   GE received broadcast frames

ge_stat_rx_vlan_frms                        0   GE received vlan frames

ge_stat_rx_pause_frms                       0   GE received pause frames

ge_err_carrier                              0   GE lost carrier sense

ge_err_length                               0   GE invalid length

ge_err_crc                                  0   GE CRC Errors

ge_err_abort                                0   GE abort frames

ge_err_overrun                              0   GE overruns

ge_err_fifo_ovf                      18350364   GE Fifo overflow

I just can't find anything on internet that could explain it.

That GE port is used for FCIP tunneling of this VE port:

> portcfgshow 16

Area Number:              16

Speed Level:              AUTO(HW)

Fill Word:                0(Idle-Idle)

AL_PA Offset 13:          OFF

Trunk Port                ON

Long Distance             OFF

VC Link Init              OFF

Locked L_Port             OFF

Locked G_Port             OFF

Disabled E_Port           OFF

Locked E_Port             OFF

ISL R_RDY Mode            OFF

RSCN Suppressed           OFF

Persistent Disable        OFF

LOS TOV enable            OFF

NPIV capability           ON

QOS E_Port                OFF

Port Auto Disable:        OFF

EX Port                   OFF

F_Port Buffers            OFF

Fault Delay:              0(R_A_TOV)

NPIV PP Limit:            126

Does anybody has any idea of where these FIFO overflow errors could come from? Could that be due to a bad setting of the BB credit on the VE port?

Thanks for your help and don't hesitate if more logs are needed.

Cheers,

Mike

Moderator
Antonio Bongiorno TechHelp24
Posts: 3,788
Registered: ‎02-23-2004

Re: GE Fifo overflow

Mike,

--->>> Does anybody has any idea of where these FIFO overflow errors could come from?

I think,.... but I'm not 100% sure, those Fifo owerflow are caused/coming from a invalid lenght, caused by to many Frame sending.

TechHelp24
Occasional Contributor
Calgada
Posts: 5
Registered: ‎10-11-2012

Re: GE Fifo overflow

Hi,

Thanks for your help. Digging a bit we're wondering if that could come from a bad MTU parameter on our tunnel.

Right now it is set at 1500 and I read that it might be worse updating it to a bit less than 2500 (provided that all the devices in the network supports jumbo frame). Is there a way of updating this parameter without recreating the entire tunnel?

Cheers,

Mike

Moderator
Antonio Bongiorno TechHelp24
Posts: 3,788
Registered: ‎02-23-2004

Re: GE Fifo overflow

--->>>Digging a bit we're wondering if that could come from a bad MTU parameter on our tunnel.

Is most probable, i facing time ago by customer same experience and the problem was wrong set MTU value.

In my case the Carrier instist first, the WAN Router was configured per default  with 1500.

we ask again and again, and later then confirm the MTU was set with another value.

Jumbo Frame shold be set enable.

TechHelp24
Occasional Contributor
Calgada
Posts: 5
Registered: ‎10-11-2012

Re: GE Fifo overflow

Thanks for your feedback.

Unfortunately, our switch is a 7800 (type 83.3) so the MTU can't be set to more than 1500...

So, I'm back to my first suggestion : changing the BB Credit value on the VE port (16) that is linked to this ge port for FCIP. It is set to 8 on this 1Gb link to a site 100km away so my guess is 50 would fit better.

But:

a) does BB credit is used on a VE port? (the GUI states that it is for F-port)

b) would changing the BB credit reset the tunnel?

c) would activating compression solve the issue?

Today, the line went so overloaded due to a DRP testing that it went down for a few seconds...

For additional information, I have attached a screenshot showing that our Storwize which is directly connected to this 7800 on ports 0-3 has some BB credit Zero timer going really high (up to 160 seconds). I take it as back pressure from the issues described precedently.

tmp.jpg

We're already planning a time slot to change the BB credit value so I'll keep you posted but I wanted to share my thoughts and the status in case someone else faces these errors.

Cheers,

Occasional Contributor
Calgada
Posts: 5
Registered: ‎10-11-2012

Re: GE Fifo overflow

Hi,

We have done the descibed changes this week-end :

- BB credit can not be changed / activated on a VE port;

- compression has been activated (moderate);

No improvement, still lots of FIFO overflow errors, Out Of Order packets, Zero BB credit timer at 190seconds... and replication group falling...

No idea what's going on so we might open a case at Brocade...

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