ftp to dev null to test bandwidth

When testing bandwidth, and troubleshooting bottlenecks, I prefer to use iperf. If you insist on testing bandwidth with FTP, it’s important NOT to use regular files. If you transfer actual files, the transfer could be limited by disk i/o, due to reads and writes. To eliminate this you can FTP from /dev/zero to /dev/null. It sounds super easy, but you have to use FTP in a special way to get it to read and write to special devices.

Here’s a little script. Be sure to replace the destination IP address, username and password with actual values:

# cat ftp_dev_null.sh
/usr/bin/ftp -n <IP address of machine> <<END
verbose on
user <usernanme> <password>
put "|dd if=/dev/zero bs=32k" /dev/null
# ftp_dev_null.sh
Verbose mode on.
331 Password required for fordodone
230 User fordodone logged in
Remote system type is UNIX.
Using binary mode to transfer files.
200 Type set to I
local: |dd if=/dev/zero bs=32k remote: /dev/null
200 PORT command successful
150 Opening BINARY mode data connection for /dev/null
send aborted
waiting for remote to finish abort
129188+0 records in
129187+0 records out
4233199616 bytes (4.2 GB) copied, 145.851 s, 29.0 MB/s
226 Transfer complete
4233142272 bytes sent in 145.82 secs (28350.0 kB/s)
221 Goodbye.

In this case I was getting around 230Mbits per second (over an IPSec tunnel) between my client and the FTP server. Not too bad.

awk multiple input field separators

We want just the last directory in the tree from this list:

# tail -3 list
/mnt/fs92/vol3/users/520/520/1680520 -- 8631
/mnt/fs92/vol3/users/568/8568/1578568 -- 2
/mnt/fs92/vol3/users/429/7429/1757429 -- 2

You can use both cut and awk, or awk twice…

# tail -3 list | cut -d / -f 8 | awk '{print $1}'

Or you can just tell awk to use multiple field separators. They are bound by square brackets, and in this case we can use both / and a space to be the input field separators, making the 8th column the one we are interested in.


# tail -3 list | awk -F "[/ ]" '{print $8}'

increase number of inodes in netapp volume

Your NetApp volume is at 85% and all is well right? What about inode usage? Don’t forget to monitor that and increase it as needed. Don’t set it too high, because inodes take up space, and you can’t shrink the number of inodes. If you do run out of inodes, you will get an autosupport, but until you provision more inodes no writes can happen on the volume. Use the maxfiles command to see how many you have as well as to increase the number.

toaster> maxfiles vol1
Volume vol1: maximum number of files is currently 35999995 (35056570 used).
toaster> maxfiles vol1 37000000