Wireshark-dev: Re: [Wireshark-dev] Packet Loss due to Disk Contention with Running Dumpcap in a
How high bandwidths are we talking about here ?
Without going to expensive higher end storage, the fastest is probably
if you can use a dedicated disk and stream directly to the raw disk.
This should avoid any of the seeks that a filesystem would induce when
writing to both file, journal and the fs metadata.
And should allow you to capture at near the peak sequential write
speed of your spindle.
regards
ronnie sahlberg
On Wed, Dec 12, 2012 at 11:33 AM, John Powell <jrp999@xxxxxxxxx> wrote:
> Hi Everyone,
>
> I am using DUMPCAP to capture packets in a high packet rate environment.
>
> My operating system is: CENTOS 6.3
>
> I am experience this problem on source compiled versions: wireshark-1.6.12
> and wireshark-1.8.4.
>
> In order to allow DUMPCAP to be run as a NON-ROOT user I am using the
> following:
>
> setcap 'CAP_NET_RAW+eip CAP_NET_ADMIN+eip' /usr/local/bin/dumpcap -v
>
> The issue is that I am experiencing packet loss to apparent disk contention
> when writing the packets to the disk - see attached file:
> packet-loss-atop.txt
>
> To help alleviate the problem I have tried the following:
>
> Disabled SELINUX
> Disabled AUDIT
> RAID 0 (striped disks) to load share the writing out of the data
>
> ARRAY /dev/md2 level=raid0 num-devices=2
> devices=/dev/sda4,/dev/sdb4
>
> Turn off journals on ext4
>
> tune2fs -o journal_data_writeback /dev/md2
> tune2fs -O ^has_journal /dev/md2
> change fstab to:
>
> UUID=.. /data ext4 defaults,data=writeback 0 0
>
> Use -B option on Dumpcap to buffer the data
>
> root /usr/local/bin/dumpcap -B 16 -i 2 -f vlan and (not vrrp and not
> udp port 1985 and not ether host 01:00:0c:cc:cc:cc) -g -b filesize:250000 -b
> duration:900 -w /data/eth1.cap
>
> These changes have increased the throughput but I still experience packet
> loss - see attached IO Graph: packet-loss-io-graph.jpg
>
> The Vendor solutions we have looked at will not decode UNISTIM signalling
> properly which is requirement for this tool.
>
> Any suggestions on how to better configure either the operating system or
> wireshark to increase packet capture throughput will be greatly appreciated.
>
> Thanks in advance for your assistance.
>
> -John
>
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