Fibre Channel (SAN)

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Occasional Contributor
Posts: 13
Registered: ‎06-25-2013

Constant increase in Time BB_Credit Zero

Hi

 

I have two long distance ISL connectivity (20km and 36km) between switches Brocade 5100 and Brocade DCX 8510-4. Initially ISL connectivity was LD:AUTO and BB credit was 86 and 150. I noticed lot of Time BB_Credit Zero and did some search found LS with static distance is best practice.

 

Based on that I defined LS with 20km with frame size 1024 and LS 36km with frame size of 1024 which automatically BB credit value of 166 and 294. While verifying port for "Time BB_Credit Zero" I can see increase in value at Brocade 5100 end but  zero value at DCX 8510-4 end. I am confused now. If there is conjestion at port end then then there should be value at both end for "Time BB_Credit Zero".

 

Here I have copied port status show of Brocade 5100 and Brocade DCX 8150-4 for 20kms link

 

Brocade 5100

Spoiler
sancbmgr03:admin> portstatsshow 13

 



 

stat_wrx                419172560   4-byte words received
stat_ftx                214334034   Frames transmitted
stat_frx                78946355    Frames received
stat_c2_frx             0           Class 2 frames received
stat_c3_frx             78853227    Class 3 frames received
stat_lc_rx              48614       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             1494683     Time TX Credit Zero (2.5Us ticks) ---> keep changing.
tim_txcrd_z_vc  0- 3:  1494683     0           0           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_rx_c3_timeout        0           Class 3 receive frames discarded due to timeout
er_tx_c3_timeout        0           Class 3 transmit 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
phy_stats_clear_ts      08-18-2014 EST Mon 09:50:41     Timestamp of phy_port stats clear
lgc_stats_clear_ts      08-18-2014 EST Mon 09:50:41     Timestamp of lgc_port stats clear

 

Spoiler
sancbmgr03:admin> portcfgshow 13

 


Area Number:              13
Speed Level:              8G
Fill Word(On Active)      0(Idle-Idle)
Fill Word(Current)        0(Idle-Idle)
AL_PA Offset 13:          OFF
Trunk Port                OFF
Long Distance             LS
VC Link Init              OFF
Desired Distance          20 Km
Frame Size                1024 Bytes
Reserved Buffers          166
Locked L_Port             OFF
Locked G_Port             OFF
Disabled E_Port           OFF
Locked E_Port             ON
ISL R_RDY Mode            OFF
RSCN Suppressed           OFF
Persistent Disable        OFF
LOS TOV enable            OFF
NPIV capability           ON
QOS Port                  OFF
Port Auto Disable:        OFF
Rate Limit                OFF
EX Port                   OFF
Mirror Port               OFF
SIM Port                  OFF
Credit Recovery           ON
F_Port Buffers            OFF
E_Port Credits            OFF
Fault Delay:              0(R_A_TOV)
NPIV PP Limit:            126
CSCTL mode:               OFF

Brocade DCX 8150-4

Spoiler
SANCDC01:admin> portstatsshow 1/0

 


stat_wtx                2229586201  4-byte words transmitted
stat_wrx                2839937044  4-byte words received
stat_ftx                181084274   Frames transmitted
stat_frx                490492745   Frames received
stat_c2_frx             0           Class 2 frames received
stat_c3_frx             490352184   Class 3 frames received
stat_lc_rx              67932       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             96          Time TX Credit Zero (2.5Us ticks) ---> this value hasn't changed for more than a week.
tim_txcrd_z_vc  0- 3:  96          0           0           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_pcs_blk              0           PCS block errors
er_rx_c3_timeout        0           Class 3 receive frames discarded due to timeout
er_tx_c3_timeout        0           Class 3 transmit frames discarded due to timeout
er_unroutable           0           Frames that are unroutable
er_unreachable          0           Frames with unreachable destination
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
er_single_credit_loss   0           Single vcrdy/frame loss on link
er_multi_credit_loss    0           Multiple vcrdy/frame loss on link
phy_stats_clear_ts      08-14-2014 EST Thu 10:56:59     Timestamp of phy_port stats clear
lgc_stats_clear_ts      08-14-2014 EST Thu 10:56:59     Timestamp of lgc_port stats clear
SANCDC01:admin>

Spoiler
SANCDC01:admin> portcfgshow 1/0

 


Area Number:              0
Octet Speed Combo:        1(8G|4G|2G)
Speed Level:              8G
AL_PA Offset 13:          OFF
Trunk Port                OFF
Long Distance             LS
VC Link Init              OFF
Desired Distance          20 Km
Frame Size                1024 Bytes
Reserved Buffers          166
Locked L_Port             OFF
Locked G_Port             OFF
Disabled E_Port           OFF
Locked E_Port             ON
ISL R_RDY Mode            OFF
RSCN Suppressed           OFF
Persistent Disable        OFF
LOS TOV enable            OFF
NPIV capability           ON
QOS Port                  OFF
Port Auto Disable:        OFF
Rate Limit                OFF
EX Port                   OFF
Mirror Port               OFF
SIM Port                  OFF
Credit Recovery           ON
F_Port Buffers            OFF
E_Port Credits            OFF
Fault Delay:              0(R_A_TOV)
NPIV PP Limit:            126
CSCTL mode:               OFF

 

Can you find or suggest what might be wrong ?

 

External Moderator
Posts: 4,779
Registered: ‎02-23-2004

Re: Constant increase in Time BB_Credit Zero

Hi,

 

it is a bit difficult to analized such error.

 

First at all, have you tried to replace the SFP's ?

 

 

TechHelp24
Valued Contributor
Posts: 520
Registered: ‎03-20-2011

Re: Constant increase in Time BB_Credit Zero

bear in mind that tim_txcrd_z can increase 400000 times per second without indicating any problems. increase of this counter simply means that "all buffers are allocated". it _doesn't_ mean "there is not enough buffers". it _doesn't_ mean "i wanted to send a frame but there was no free buffer so i had to wait". however, it _could_ as well mean all of this, but then you would also see increasing discards.

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