[dm-crypt] unusual writing speeds when benchmark speeds are high enough

.. ink .. mhogomchungu at gmail.com
Sun Mar 17 22:36:19 CET 2013


Sorry for my previous email without a title,resending the email with a
title this time.

A user of cryptsetup(through zuluCrypt) asked me a question i can not
answer and asking it here.

In his system,"cryptsetup benchmark" gives the following results:

[root <at> sheep 13] ~ > cryptsetup benchmark
# Tests are approximate using memory only (no storage IO).
PBKDF2-sha1       341333 iterations per second
PBKDF2-sha256     193607 iterations per second
PBKDF2-sha512      64125 iterations per second
PBKDF2-ripemd160  303758 iterations per second
PBKDF2-whirlpool   64125 iterations per second
#  Algorithm | Key |  Encryption |  Decryption
     aes-cbc   128b   183,6 MiB/s   215,4 MiB/s
 serpent-cbc   128b    68,0 MiB/s    68,9 MiB/s
 twofish-cbc   128b   167,7 MiB/s   177,5 MiB/s
     aes-cbc   256b   142,3 MiB/s   161,5 MiB/s
 serpent-cbc   256b    69,7 MiB/s    67,0 MiB/s
 twofish-cbc   256b   170,1 MiB/s   177,8 MiB/s
     aes-xts   256b   201,2 MiB/s   205,6 MiB/s
 serpent-xts   256b    69,7 MiB/s    67,6 MiB/s
 twofish-xts   256b   180,5 MiB/s   175,6 MiB/s
     aes-xts   512b   147,0 MiB/s   152,5 MiB/s
 serpent-xts   512b    70,5 MiB/s    67,8 MiB/s
 twofish-xts   512b   182,0 MiB/s   176,0 MiB/s

The system is decent enought.

The write speed he is getting though through the mapper is unusually
slow,the test is below:


[root <at> sheep 8] ~ > dd if=/dev/zero of=test.img bs=70M count=1
1+0 Datensätze ein
1+0 Datensätze aus
73400320 Bytes (73 MB) kopiert, 2,58497 s, 28,4 MB/s

[17.03.2013 21:50 Uhr]
[root <at> sheep 9] ~ > cryptsetup create test test.img
Passsatz eingeben:

[17.03.2013 21:51 Uhr]
[root <at> sheep 10] ~ > dd if=/dev/zero of=/dev/mapper/test bs=10M count=1
1+0 Datensätze ein
1+0 Datensätze aus
10485760 Bytes (10 MB) kopiert, 67,2014 s, 156 kB/s

[17.03.2013 21:52 Uhr]
[root <at> sheep 11] ~ > cryptsetup remove test

As the test show,He is getting 156kB/s when using dd over the encryption
mapper verses 28MB/s when using dd straight.

Where is the wrong in his system? version of cryptsetup used is 1.6.0
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.saout.de/pipermail/dm-crypt/attachments/20130317/67e21f17/attachment.html>


More information about the dm-crypt mailing list