FTP Tuning for T64 5.1A

[Eduardo E. Silva]

We have a DS20 with 2.256 GB of RAM an Intel dual NIC (10/100) and a (KZPSC-XB) xcr0 raid control with three digital scsi disk trays. When we transfer lots of data (20GB+) over an private LAN ( two Alphas connected with crossover cable) the system comes down to a crawl -- CPU is idle, disk lights solid green.

I have notice that the disks seem the bottle neck and the ftp transfer come to a wait state while the disks are still writing data. Their green leds are solid while the ftp transfer is going on.

The NICs are set to 100Mbs full duplex.

What do I need to set in the kernel to help the disks keep up with the NIC speed. There are no errors from the netstat command.

Ed Silva
esilva@silvex.com

[Han Pilmeyer]

There are lots of things that could play a role here. Good time start from the bottom up with your investigations. Since you already suspect it has something to do with disk I/O, you might as well start there.

- Look for the activity on the disks (iostat or collect) and see whether that makes sense.
- Since you're transferring large quatities of data (20 GB+), the file system may be struggling to find enough free space. If this is on AdvFS, see what defragment thinks about this.
- FTP is typically not a good program to transfer data in a fast way. This is especially true if the data is transferred in lots of small files. As an experiment, see whether writing local data goes any faster (you could "make up" the data by using something like /dev/zero) or whether it is any faster to store the data when it arrives in a "single stream" (e.g. use tar and pipe the stream to the remote system using rsh/ssh and then store the tar container without unpacking it).

Hope this gives you an idea where to start.

[Ralf Puchner]

use sys_check to get a primary analyze of your speeds and tuning suggestions. Be sure you understand each parameter and doublecheck prior to correct the value within sysconfigtab.