Re: Packet Loss due to Disk Contention with Running Dumpcap in a high packet rate environment

[Richard Sharpe <realrichardsharpe () gmail com>]

On Thu, Dec 13, 2012 at 8:59 AM, John Powell <jrp999 () gmail com> wrote:
> Hi Ronnie,
>
> I am capturing a 250 MB file every few seconds.  My ATOP reports:
>
> MDD |          md2 | busy      0% | read       1  | write  15442 | KiB/r
> 4 | KiB/w      4 | MBr/s   0.00 | MBw/s  60.32  | avq     0.00 | avio 0.00
> ms |
> DSK |          sda | busy    107% | read       1  | write    205 | KiB/r
> 4 | KiB/w    506 | MBr/s   0.00 | MBw/s 101.33  | avq    93.88 | avio 4.51
> ms |
> DSK |          sdb | busy     92% | read       0  | write    191 | KiB/r
> 0 | KiB/w    511 | MBr/s   0.00 | MBw/s  95.50  | avq    86.84 | avio 4.20
> ms |
>
> I need the resulting files to be searchable by TSHARK and be able to create
> a PCAP extraction based on the search.
>
> The dumpcap command being used is:
>
> usr/local/bin/dumpcap -B 16 -i 4 -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/eth2.cap
>
> I am looking at using a SSD for my OS and my Capture volume which may help
> out with the Disk IO issue but eliminating the copy from the /TMP would
> definitely be an asset.

That sounds like about 100MB/s.

If you can use a file system like XFS that can separate metadata from
data, and put your metadata on SSD, then you might find that a small
array of spinning disks is enough for you.

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)
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