[dm-crypt] Re : Poor performances with nfs and Kernel 3.x

Mickael mki2268 at yahoo.com
Wed Feb 8 15:55:20 CET 2012


> À : dm-crypt at saout.de
>  Cc : 
>  Envoyé le : Mardi 7 février 2012 9h11
>  Objet : Re: [dm-crypt] Poor performances with nfs and Kernel 3.x
> 
> On Mon, Feb 06, 2012 at 10:28:24PM +0000, Mickael wrote:
>> Hello,
>>
>> I'm writing about poor performances accessing a dm-crypt/LUKS partition
>> using nfs.
>> 
>> I was running a fileserver Ubuntu_Server_11.04 (Kernel 2.6.38-13#52) with
>> no problem.  But after an upgrade to Ubuntu_Server_11.10 (Kernel
>> 3.0.0-15#26) reading and writing a crypted partition with nfs is very
>> slow.
>
>Interesting. I think have no issues here with Debian stable and Kernel
>3.2.2 on the server and 3.1.6 on the client. 
>
>What is the kernel version on your client?

My client is an Unbutu 3.0.0-15#26 amd64 (2 CPU)
Results are the same, using a 2.6 or 3.0 Kernel on the client.
The problem seems to be located on the server only

>3.0.0 is not a very good kernel though with a number of issues. 
>There is also a local privilege excalation in 3.x that has been 
>fixed only in 3.2.2 and later. (Unless Ubuntu did it.)

I've build a Fedora 16 (3.2.1-3) with no change
I need to find a distro with a recent Kernel (>3.2.2) to test if it solve the problem

>
>> 
>> I've made different tests with a 2GB file to show the difference when the
>> server is running a 2.6 or 3.0 kernel.  All others parameters are always
>> the same.
>> 
>> First, a test using nfs to access a crypted partition (dm-crypt/LUKS/ext4)
>> on the server:
>>
>> *Svr Kernel 3.0.0-15#26? : NFS (R/W) = 30 MB/s / 33 MB/s?? <-------- The problem is here !
>> *Svr Kernel 2.6.38-13#52 : NFS (R/W) = 81 MB/s / 53 MB/s
>>
>> As you can see, with the Kernel 3.0, performances are very bad. The flow
>> is always constant at ~30MB; there's clearly a limitation
>
>What did you use to do the benchmark? 

Just coying a 2GB avi file with
time cp /tmp/testfile.avi /mnt/CRYPT/
and calculate the average speed (2000MB/time_sec)


>
>> For comparison, the same test, but this time, using nfs to read and write
>> a non-crypted partition (ext4) (same HD of the crypted partition):
>>
>> *Svr Kernel 3.0.0-15#26? : NFS (R/W) = 92 MB/s / 77 MB/s
>> *Svr Kernel 2.6.38-13#52 : NFS (R/W) = 111 MB/s / 74 MB/s
>> Using nfs without dm_crypt, performances are good with the 2 Kernels
>
>Interesting.
>
>I will do a benchmark here and see whether I have the same.
>
>Arno
>
>------ Cut ------
>
>-- 
>Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
>GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
>----
>One of the painful things about our time is that those who feel certainty 
>are stupid, and those with any imagination and understanding are filled 
>with doubt and indecision. -- Bertrand Russell 
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