Fibre Channel (SAN)

Reply
New Contributor
Posts: 3
Registered: ‎01-30-2013

counters tim_txcrd_z increase

Hi,

 

see below  : 

For information, this port is not an ISL

 

switch admin> portstatsshow 4
stat_wtx 3297406945 4-byte words transmitted
stat_wrx 2256674145 4-byte words received
stat_ftx 19469329 Frames transmitted
stat_frx 21954638 Frames received
stat_c2_frx 0 Class 2 frames received
stat_c3_frx 21954638 Class 3 frames received
stat_lc_rx 0 Link control frames received
stat_mc_rx 0 Multicast frames received
stat_mc_to 0 Multicast timeouts
stat_mc_tx 0 Multicast frames transmitted
tim_rdy_pri 0 Time R_RDY high priority
tim_txcrd_z 9724978 Time TX Credit Zero (2.5Us ticks)
tim_txcrd_z_vc 0- 3: 0 0 9724978 0
tim_txcrd_z_vc 4- 7: 0 0 0 0
tim_txcrd_z_vc 8-11: 0 0 0 0
tim_txcrd_z_vc 12-15: 0 0 0 0
er_enc_in 0 Encoding errors inside of frames
er_crc 0 Frames with CRC errors
er_trunc 0 Frames shorter than minimum
er_toolong 0 Frames longer than maximum
er_bad_eof 0 Frames with bad end-of-frame
er_enc_out 0 Encoding error outside of frames
er_bad_os 0 Invalid ordered set
er_c3_timeout 0 Class 3 frames discarded due to timeout
er_c3_dest_unreach 0 Class 3 frames discarded due to destination unreachable
er_other_discard 0 Other discards
er_type1_miss 0 frames with FTB type 1 miss
er_type2_miss 0 frames with FTB type 2 miss
er_type6_miss 0 frames with FTB type 6 miss
er_zone_miss 0 frames with hard zoning miss
er_lun_zone_miss 0 frames with LUN zoning miss
er_crc_good_eof 0 Crc error with good eof
er_inv_arb 0 Invalid ARB
open 0 loop_open
transfer 0 loop_transfer
opened 0 FL_Port opened
starve_stop 0 tenancies stopped due to starvation
fl_tenancy 0 number of times FL has the tenancy
nl_tenancy 0 number of times NL has the tenancy
zero_tenancy 0 zero tenancy

New Contributor
Posts: 3
Registered: ‎01-30-2013

Re: counters tim_txcrd_z increase

Why this counter increases?
An idea for resolve this issue

Regular Contributor
Posts: 164
Registered: ‎05-11-2011

Re: counters tim_txcrd_z increase

Hi Fabien,

 

if this port is an Storage Port, the Storage may not be able to handle the I/O s in an acceptable time.

The port runs out of BB-Credits.

 

 

Kind Regards
Ralf
New Contributor
Posts: 3
Registered: ‎01-30-2013

Re: counters tim_txcrd_z increase

Hi Ralph,

 

Thanks for reply.

 

Are there a command for increase BB, or not ?

 

 

Eli
Contributor
Posts: 30
Registered: ‎03-14-2012

Re: counters tim_txcrd_z increase

Hi,

Each frame can "live" in the queue 2.5us, and after this timeout the frame discarded.

There are few things that can cause the issue:

1. Slow Drain devices - the devices cant handle such amount of IO, so the frames are "dead" in the queue.

2. Replace the path to the device: HBA, fiber, patch panel etc.

Frequent Contributor
Posts: 80
Registered: ‎01-28-2010

Re: counters tim_txcrd_z increase

[ Edited ]

it would be interesting to know, how fast does the counter increase

 

tim_txcrd_z
The number of times that the port was unable to transmit frames because the transmit BB credit was zero. The purpose of this statistic is to detect congestion or a device affected by latency. This parameter is sampled at intervals of 2.5 microseconds, and the counter is incremented if the condition is true. Each sample represents 2.5 microseconds of time with zero Tx BB Credit. An increment of this counter means that the frames could not be sent to the attached device for 2.5 microseconds, indicating degraded performance.
 
2.5 microseconds * 400 000 = one minute
if you hit the 400k mark your link is bottlenecked and has no possibility to transmit frames.
 
aktion you could do to determine the status of the port--->>
 

first clear the portstats with portstatsclear #portnumber

then issue portstatsshow #portnumber and about one minute later reissue the same command again.

if you have a never FOS on the switch you have a timestemp, if the FOS is older then you need to see how much the counter did increase within the one minute,

 

 if the counter increases 400 000 units per minute you have a problem.

 

--if this is a storage port you have to much hosts on it and need to recheck mapping/utilisation and a possbile remap to a different storageport, would be the first guess,

 

if not then you have other issues that you need to have a look into.

 

for the start let us know how fast does the counter increase, whats behind the port

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: counters tim_txcrd_z increase

Hi,

 

in response to your query,

 

Are there a command for increase BB, or not ?

 

The answer is no, at least on the switch: the number of TX BB credits is stablished by the device at the other side of the link. If it were another switch (ISL), then you could increase the amount of BB credits (Extended Fabric licence required). But if it is a host or storage array, there is no way that I know to increase the number of BB. If you are experiencing performance issues due to this you should add more hbas to the host and/or spread the load among more ports in the storage array.

 

 

rgds

Frequent Contributor
Posts: 107
Registered: ‎04-05-2011

Re: counters tim_txcrd_z increase


felipon wrote:

Hi,

 

in response to your query,

 

Are there a command for increase BB, or not ?

 

The answer is no, at least on the switch: the number of TX BB credits is stablished by the device at the other side of the link. If it were another switch (ISL), then you could increase the amount of BB credits (Extended Fabric licence required). But if it is a host or storage array, there is no way that I know to increase the number of BB. If you are experiencing performance issues due to this you should add more hbas to the host and/or spread the load among more ports in the storage array.

 

 

rgds


At least on FOS v6.4.1 and newer, it is possible to increase the number of bb credits on F_Ports. you can use the portcfgfportbuffers

 

 

CTI_CORP:sag> portcfgfportbuffers
Usage:   portCfgFportBuffers Mode [Slot/]Port [Buffers]
Mode:    --disable - F_Port will use the default number buffers
         --enable  - F_Port will use the value 'Buffers' for number buffers
CTI_CORP:sag> firmwareshow
Appl     Primary/Secondary Versions
------------------------------------------
FOS      v6.4.1a
         v6.4.1a

 

Valued Contributor
Posts: 761
Registered: ‎06-11-2010

Re: counters tim_txcrd_z increase

@anovelli, that command increases the amount of RX BB credits but it doesn't modify the amount of TX BB credits that is the one monitored by counter tim_txcrd_z.

 

rgds,

Felipon

Frequent Contributor
Posts: 107
Registered: ‎04-05-2011

Re: counters tim_txcrd_z increase

Hi Felipon!

 

In my understanding, the number of buffer credits must be the same on both sides of the fibre. what portcfgfportbuffers do is to enable you to do this matching to better use the buffer capability of the hosts/storages attached to that port. For example, some emulex HBAs have 16 buffer credits enabled for a certain framesize and the default f port buffers on the switch is 8 so if i see bbcredit errors raising on the switch, i can increase the f-port buffers and in my case, it solved the problem.

 

 

Join the Community

Get quick and easy access to valuable resource designed to help you manage your Brocade Network.