Determining Hardware capacity

Unanswered Question
Mar 5th, 2010

Hello,

The backbone of my network consists of a pair of 4507R with Sup-IV. My servers all connect to 4507s via the WS-X4548-GB-RJ45 line cards. From what I was reading, this is not the best choice of line card for connecting many high-bandwidth servers due to the 8:1 over subscription. I know the cards are becoming overwelmed at times and i'm looking for a way to quanify this.

What stats can I look at to proove that the line cards are becoming overwhelmed due to the servers trying to consume too much bandwidth?

Can I use the "Total Output Drops" counters? Is there some other kind of output I can use to quantify how these cards are performing? Thanks.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
rtjensen4 Fri, 03/05/2010 - 11:11

Hi Edison,

Is this the same CiscoView i can get via Cisco Works? I'm assuming so yes?

I don't see how this will show me like ASIC utilization or some measure of dropped packets due to ASIC saturation.

Giuseppe Larosa Fri, 03/05/2010 - 13:29

Hello,

yes output drops in the 8 ports group is a clear sign of the oversubscription effect on WS-4548, but they don't count all of these drops.

It should be enough to demonstrate the problem but it doesn't provide a precise measure of how many frames are dropped.

For us it was enough to demonstrate to management that these linecards are not good in modern GE server farms

see also the following document:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a008015bfd6.shtml#oversub

>>If the frames received on any group exceeds the bandwidth of 1 Gbps,       the device starts to drop the frames. These drops are not obvious as they are       dropped at the internal ASIC rather than the actual interfaces. This can lead       to slow throughput of packets across the device.

The Rx-No-Pkt-Buff does not depend on the total traffic rate. It       depends on the amount of the packets that are stored in the Rx FIFO buffer of       the module ASIC. The size of this buffer is only 16 KB. It is counted with       short bursty traffic flows when some packets fill this buffer. Thus,       Rx-No-Pkt-Buff on each port can be counted when the total traffic rate of this       ASIC port group exceeds 1 Gbps, since WS-X4548-GB-RJ45 is 8:1 oversubscribed       module.

Hope to help

Giuseppe

Actions

This Discussion