As I understand the man-Page of bonnie++ it says that "-s indicates the size of the file(s) for IO performance measures in megabytes...". So it should be 4000 MB. Sorry, I forgot to state that in the mail. Thanks for the hdparm suggestion I will set hdparm and run the test again. Gisle Sælensminde wrote: > Markus Huehnerbein wrote: >> Hi List, >> >> I did some performance tests using the benchmark bonnie++ to evaluate >> different disk encryption possibilities. The results regarding loop-aes >> are a bit strange for my understanding. I ran the tests on a notebook >> with Debian Etch, 1GB RAM and a Linux 2.6.22.2 Kernel. >> >> Bonnie was startet with the following parameters: >> bonnie++ -b -u root -s 4000 >> >> As a result loop-aes has a sequential input (block) of 29127 K/sec where >> the sequential input with no encryption is 25123 K/sec. The same with >> sequential output (block) (loop-aes: 27633 K/sec and no encryption: >> 24267 K/sec). >> >> What I don't understand is how encrypted reads and writes per block >> could be faster as plaintext reads / writes? Any comments are welcome! >> >> > Now I know very little about the bonnie++ benchmark, but it says that > > 4MB is way to little to show anything. Factors like caching and process > overhead (which benchmark did you run first?) and other similar factors > will dominate. Try with at least 4GB. Since the bonnie program test for > database-like access according to it's website, it will probably not > make much sense before you test it with file sizes significantly larger > than the main memory. > > If you have not set hdparm, sometimes DMA is not used by the kernel. > This is the safest on some buggy (but common) mainboards, and may be the > default on your system. If this is set, non-encrypted writing will be > much slower than it need to be. Read the manual page for hdparm. > > With DMA enabled, the null cipher (that is no encryption) can be as slow > as an encrypted filesystem, because what slows things down is that the > block has to be copied into RAM. > >> Kind regards, >> Markus >> >> P.S.: The bonnie++ output: >> LOOP-AES: >> ------Sequential Output------ --Sequential Input- --Random- >> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- >> Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP >> 4000M 18554 59 27633 7 13696 3 18922 77 29127 4 102.3 0 >> >> NO ENCRYPTION: >> ------Sequential Output------ --Sequential Input- --Random- >> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- >> Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP >> 4000M 24085 77 24267 6 11978 3 24825 75 25123 3 103.9 0 >> >> >> - >> Linux-crypto: cryptography in and on the Linux system >> Archive: http://mail.nl.linux.org/linux-crypto/ >> >> > - Linux-crypto: cryptography in and on the Linux system Archive: http://mail.nl.linux.org/linux-crypto/
