disk

Benchmarking an encrypted dm-crypt/LVM/ext3/SELinux hard drive with bonnie++ and hdparm

I'm going to set up a new laptop system soonish (more on that later) which shall have a completely encrypted hard drive. Hence, I'm testing a few setups wrt security, performance, manageability and fault-tolerance.

Here's a few performance tests I did on an 80 GB laptop hard drive (in an Intel Celeron based laptop, 1.7 GHz, 256 MB RAM, Linux 2.6.17, Debian unstable).
I ran bonnie++ (with no options) and hdparm as hdparm -tT /dev/hda each time. I haven't put too much thought into the test setup, so if I made some stupid mistakes, please let me know.

Unencrypted plain ext3 partitions:

  • Extra partitions for /, /boot, /usr, /var, /tmp, /home, and swap (no LVM).
  • Optionally, SELinux enabled on that system (targeted policy in permissive mode).

bonnie++:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
forest         432M 19857  84 21831  10  9536   4 16355  58 22165   3 148.8   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  1650  98 +++++ +++ +++++ +++  1734  98 +++++ +++  3820  96
forest,432M,19857,84,21831,10,9536,4,16355,58,22165,3,148.8,0,16,1650,98,+++++,
+++,+++++,+++,1734,98,+++++,+++,3820,96

bonnie++ with SELinux:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
forest         432M 20321  90 21036  13  9473   5 16742  61 21978   4 148.1   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  1398  98 +++++ +++ +++++ +++  1473  98 +++++ +++  3305  98
forest,432M,20321,90,21036,13,9473,5,16742,61,21978,4,148.1,0,16,1398,98,+++++,
+++,+++++,+++,1473,98,+++++,+++,3305,98

hdparm:

 Timing cached reads:   1416 MB in  2.00 seconds = 707.48 MB/sec
 Timing buffered disk reads:   82 MB in  3.06 seconds =  26.80 MB/sec

hdparm with SELinux:

 Timing cached reads:   1404 MB in  2.00 seconds = 700.59 MB/sec
 Timing buffered disk reads:   80 MB in  3.02 seconds =  26.53 MB/sec

Ext3 partitions on top of LVM on top of dm-crypt:

  • One partition which is encrypted using dm-crypt (aes-cbc-essiv:sha256 mode, AES, 256 bit key size)
  • On top of that an LVM2 system, with extra partitions for /, /boot, /usr, /var, /tmp, /home, and swap.
  • Optionally, SELinux enabled on that system (targeted policy in permissive mode).

bonnie++:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
forest         464M 11149  54 16660  20  6461   5  7472  58 11129   5 136.4   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  1564  98 +++++ +++ +++++ +++  1650  98 +++++ +++  2640  97
forest,464M,11149,54,16660,20,6461,5,7472,58,11129,5,136.4,0,16,1564,98,+++++,
+++,+++++,+++,1650,98,+++++,+++,2640,97

bonnie++ with SELinux:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
forest         464M  9878  52 12138  11  5457   6  6834  56 11037   5 137.2   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  1426  97 +++++ +++ +++++ +++  1451  98 +++++ +++  2433  97
forest,464M,9878,52,12138,11,5457,6,6834,56,11037,5,137.2,0,16,1426,97,+++++,
+++,+++++,+++,1451,98,+++++,+++,2433,97

hdparm:

 Timing cached reads:   1408 MB in  2.00 seconds = 704.01 MB/sec
 Timing buffered disk reads:   80 MB in  3.02 seconds =  26.53 MB/sec

hdparm with SELinux:

 Timing cached reads:   1396 MB in  2.00 seconds = 698.06 MB/sec
 Timing buffered disk reads:   82 MB in  3.07 seconds =  26.69 MB/sec

So yes, there is some overhead, but it's nothing too serious, IMHO. And quite honestly, I don't care too much about performance here — security is more important than performance. I think you'll agree; if you don't agree now, you will agree with me on the very day someone steals your laptop ;-)

Stupid question of the day

Are full hard drives heavier than empty hard drives?

I read about this in the Talk page of the article about disk drives in the German Wikipedia.

What sounds like a pretty stupid question (it probably is), might still have a pretty interesting answer. Any physics students (electrical engineering? computer science?) out there who can enlighten us? Are there any scientific studies about such issues? There are some theories (German, sorry), but I'm not sure whether that's more than random guesses...

Other stupid questions from the articles above: Are charged cell phone batteries heavier than empty ones? Are Word documents with bigger fonts heavier?

My head hurts...

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