LINUX - HOW TO TEST REAL SPEED OF DRIVES WITHOUT CACHING

HOW TO TEST REAL SPEED OF DRIVES WITHOUT CACHING
################################################

Create a ram disk which is a big portion of RAM and fill it up. Then test the regular disks speed. No need

Without filling up RAM Disk:
dd if=/dev/zero of=/root/asdfasd bs=1M
1 GB /s

cat /proc/meminfo
free -m
Shows I have 512 MB ram

Lets make a ram disks of 450 MB size
mkdir /ramdisk
mount -t tmpfs -o size=450M ramfs /ramdisk/

Fill it up to 99%
dd if=/dev/zero of=/ramdisk/fillupfile bs=1M count=449
2.9 GB/s
Thats just the speed of the RAM
Now that /ramdisk is pretty full, the memory should be pretty empty now
To confirm
free -m

I have about 20GB free space on /root directories filesystem. Lets write a 5 GB file.
dd if=/dev/zero of=/root/testfile bs=1M count=5000
500 MB/s

So thats the true speed without ram caching - maybe a little bit of ram caching
To free up ram, just unmount the ramdisk - its a property of the ramdisk to delete whatever is in it when ever its unmounted. If its not deleted it will be left as available space for other things.

You can use:
top
And:
free -m

To monitor @ at any time.
SelectionFile type iconFile nameDescriptionSizeRevisionTimeUser
Comments