LinuxQuestions.org - ext4 slower than ext3

I have a 6 disk machine, i am using FC12, i created a software raid 5 device /dev/md1

i formatted it

Code:

mkfs.ext4 /dev/md1

and mounted with options as so:

Code:

/dev/md1 on /usr/local type ext4 (rw,noatime,user_xattr)

i then ran dd to see how fast i can write to it:

Code:

dd if=/dev/zero of=/usr/local/test.out bs=512k count=20k

20480+0 records in

20480+0 records out

10737418240 bytes (11 GB) copied, 77.4035 s, 139 MB/s

I did this a number of times and got similar speeds - 139MB/s each time.

I then unmounted and did mkfs.ext3 /dev/md1

and mounted again like so:

Code:

/dev/md1 on /usr/local type ext3 (rw,noatime,user_xattr)

Code:

dd if=/dev/zero of=/usr/local/test.out bs=512k count=20k

20480+0 records in

20480+0 records out

10737418240 bytes (11 GB) copied, 44.3047 s, 242 MB/s

I did it a number of times, always around 240MB/s

I guess I will stick with ext3

However, I would be very interested to know *why* the newer filesystem is slower, and by so much!

many thanks