LUKS ext4 performance

This time I want to compare performance of LVM based ext4 filesystem with LUKS encrypted device created on the same LVM volume.
Test system is intel cd2 e8200, 6GB RAM, 4*ST31500341AS (seagate 7200.11, 1.5TB) soft raid5.
First result is notcrypted LVM with ext4 filesystem:

Then same volume but encrypted with 128bit AES:

And last result for LUKS encrypted LVM volume with 256bit AES:

Seems that performance loss is very big. 256bit AES volume have 3 times slower write speed, almost 2.5 times slower read speed and more than 2 times slower rewrites.
128bit AES volume is a bit faster than 256bit one, but it's still more than 2 times slower in writes and almost 2 times slower in reads and rewrites than notcrypted one.
Looks like there is small difference between 128 and 256 modes, so I vote for 256 one which is considered much more secure.
CPU load is lower for both encrypted volumes than unencrypted one, but this CPU load is only load connected with I/O operations (iowaits). This is not CPU load connected
with encryption. CPU load is lower for encrypted volumes, cause there is less data to read and write in the same amount of time. But CPU is loaded more during tests with encrypted
volumes cause almost whole core power is taken by encryption process.

Core2Duo doesn't have AES instructions. I wonder how this looks on machine with AES extension and I hope I'm gonna test it tommorow :).

Read performance of 256bit encrypted volume is not bad for desktop work (this is my HTPC), who need more it such enviroment? But write performance lower than 1Gbps is dissapointing.
Stragne thing is that the fastest seeks are on 256bit volume, it's like 25% faster than unencrypted one.

So you should decide what you want, secure files or very good performance without encryption. I choose first :).

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Article | by Dr. Radut