Bandwidth testing

Units

For these measurements:

• 1 kB/s = 1,000 bytes per second
• 1 mB/s = 1,000,000 bytes per second
• 1 gB/s = 1,000,000,000 bytes per second

Machines tested

machine name	processor speed	memSize	10 files of size	dd /dev/zero to /dev/shm	cp /dev/shm to /tmp	cp /dev/shm to hive	rsync /dev/shm to /dev/shm
hgwdev	Opteron 1150 Mhz	32 Gb	1 gB	800 mB/s	287 mB/s	54 mB/s	144 mB/s
kolossus	Intel 2261 Mhz	1 Tb	1 gB	1980 mB/s	192 mB/s	41 mB/s	120 mB/s 4X rsync
okazaki	Intel 1600 Mhz	2 Gb	76 mB	700 mB/s	90 mB/s	11.3 mB/s	11.5 mB/s
mitzie	Intel 400 Mhz	512 Kb	18 mB	113 mB/s	25 mB/s	n/a	37 kB/s up down

Procedure

Sizing files based on available /dev/shm space. Largest file size limited to 1 gB.

The /dev/zero to /dev/shm write is done ten times with a dd command:

 dd if=/dev/zero of=/dev/shm/memToMem.$I.zero bs=200000 count=$ddCount

The /dev/shm copy to /tmp is done ten times with the cp command:

cp -p /dev/shm/memToMem.$I.zero ./memToFile.$I.zero

These 10X copies were repeated three times. The slowest measurement of the three times was recorded.

The rsync /dev/shm to /dev/shm was to and from hgwdev. Multiple instances of rsync from kolossus to hgwdev seemed to add together for a total bandwidth higher than a single instance of rsync.

The machine mitzie is at the end of a Santa Cruz DSL line and over a WiFi network connection across the driveway to the garage.