Cisco DS-C9124-K9 Troubleshooting Guide - Page 429

Chapter 20 Troubleshooting IP Storage Services iSCSI TCP Performance Issues Send documentation comments to [email protected] 5 minutes output rate 609420144 bits/sec, 76177518 bytes/sec, 53267 frames/sec 6979248 packets input, 514206826 bytes 0 multicast frames, 0 compressed 0 input errors, 0 frame, 0 overrun 0 fifo 55551272 packets output, 79456286344 bytes, 0 underruns 0 output errors, 0 collisions, 0 fifo 0 carrier errors Better throughput can be achieved if the MTU of both the client NIC and the IPS Gigabit Ethernet interface is changed to a higher MTU, provided the network in the middle supports jumbo frames. Use the show ips stats tcp CLI command to view TCP statistics (see Example 20-3). If the retransmitted value in the segment continues to increase, it shows that either the IP network in the middle has issues or the TCP peer has problems acknowledging the data that the IPS sends to it. If the MTU of this interface is higher than the MSS of the iSCSI client, then the split packets value increases. For example, the client MTU default is 1500, which equates to an MSS value of 1460, but the IPS Gigabit Ethernet MTU changed to 2500. Example 20-3 show ips stats tcp Command Output MDS_BOTTOM# show ips stats tcp interface gigabit 2/1 detail TCP Statistics for port GigabitEthernet2/1 TCP send stats 56252632 segments, 76746280484 bytes 56100434 data, 152173 ack only packets 1 control (SYN/FIN/RST), 0 probes, 24 window updates 0 segments retransmitted, 0 bytes 0 retransmitted while on ethernet send queue, 0 packets split 3 delayed acks sent TCP receive stats 7068115 segments, 1061853 data packets in sequence, 54245464 bytes in sequence 0 predicted ack, 187 predicted data 0 bad checksum, 0 multi/broadcast, 0 bad offset 0 no memory drops, 0 short segments 0 duplicate bytes, 0 duplicate packets 0 partial duplicate bytes, 0 partial duplicate packets 0 out-of-order bytes, 0 out-of-order packets 0 packet after window, 0 bytes after window 0 packets after close 7067879 acks, 76746255713 ack bytes, 0 ack toomuch, 21 duplicate acks 0 ack packets left of snd_una, 0 non-4 byte aligned packets 5980106 window updates, 0 window probe 50 pcb hash miss, 0 no port, 0 bad SYN, 0 paws drops TCP Connection Stats 0 attempts, 24 accepts, 24 established 22 closed, 2 drops, 0 conn drops 0 drop in retransmit timeout, 0 drop in keepalive timeout 0 drop in persist drops, 0 connections drained TCP Miscellaneous Stats 7054414 segments timed, 7067879 rtt updated 0 retransmit timeout, 0 persist timeout 19 keepalive timeout, 19 keepalive probes TCP SACK Stats 0 recovery episodes, 54218621 data packets, 77791012992 data bytes 0 data packets retransmitted, 0 data bytes retransmitted 1 connections closed, 0 retransmit timeouts TCP SYN Cache Stats 24 entries, 24 connections completed, 0 entries timed out 0 dropped due to overflow, 0 dropped due to RST 0 dropped due to ICMP unreach, 0 dropped due to bucket overflow OL-9285-05 Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x 20-55