SAS 6/iR write performance depends on kernel version, blade server m600

Dominique LALOT dom.lalot at gmail.com
Mon Jun 2 07:47:17 CDT 2008


I have some more information about kernel version

To be more precise: I/O writes are OK till 2.6.21. The problem appears 
in 2.6.22. I compiled more than 20 kernels since a few weeks now. 
Hopefully, the hardware is very fast except that I/O problem.

debian-test:/usr/src# uname -a
Linux debian-test.pr.univmed.fr 2.6.22.1 #1 SMP Mon Jun 2 12:03:44 CEST 
2008 i686 GNU/Linux
debian-test:/usr/src# dd if=/dev/zero of=/root/test.cdrom bs=10k count=60000
60000+0 enregistrements lus
60000+0 enregistrements écrits
614400000 octets (614 MB) copiés, 8,10601 seconde, 75,8 MB/s
debian-test:/usr/src# time tar -xzf linux-2.6.24.tar.gz

real    0m9.740s
user    0m2.732s
sys     0m1.520s
debian-test:/usr/src# dmesg | grep -i write
sd 4:1:0:0: [sdb] Write Protect is off
sd 4:1:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA
sd 4:1:0:0: [sdb] Write Protect is off
sd 4:1:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA


debian-test:~# uname -a
Linux debian-test.pr.univmed.fr 2.6.21.7 #1 SMP Fri May 30 18:39:58 CEST 
2008 i686 GNU/Linux
debian-test:~# dd if=/dev/zero of=/root/test.cdrom bs=10k count=60000
60000+0 enregistrements lus
60000+0 enregistrements écrits
614400000 octets (614 MB) copiés, 1,21061 seconde, 508 MB/s
debian-test:~#
debian-test:/usr/src# time tar -xzf linux-2.6.24.tar.gz

real    0m2.602s
user    0m2.544s
sys     0m1.508s

debian-test:~# dmesg | grep -i write
sda: Write Protect is off
SCSI device sda: write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA
sda: Write Protect is off
SCSI device sda: write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA
I'm not sure now that the problem comes from that string. The string has 
been changed/added recently



Alessandro FAGLIA a écrit :
> -------- Original Message  --------
> Subject: Re: SAS 6/iR write performance depends on kernel version, blade 
> server m600
> From: Dominique LALOT <dom.lalot at gmail.com>
> To: Alessandro FAGLIA <a.faglia at farmol.it>, linux-poweredge at dell.com
> Date: Fri May 30 2008 10:34:05 GMT+0200 (ora legale Europa occidentale)
>   
>> Alessandro FAGLIA a écrit :
>>     
>>> -------- Original Message  --------
>>> Subject: SAS 6/iR write performance depends on kernel version, blade 
>>> server    m600
>>> From: Dominique LALOT <dom.lalot at gmail.com>
>>> To: linux-poweredge at dell.com
>>> Date: Mon May 19 2008 16:05:10 GMT+0200 (ora legale Europa occidentale)
>>>       
>>>> Hello,
>>>>
>>>> That's quite a long time, I'm "playing" around a performance problem.
>>>>
>>>> We just acquire some  new blades and  I discovered something strange 
>>>> affecting the new SAS 6 subsystem.
>>>>
>>>> [...]
>>>>
>>>>         
>>> Good morning Mr Lalot.
>>>
>>> I'm a Linux-PE ML reader, and we are buying two new R300 server with 
>>> SAS 6iR RAID controller. We'd like to use them in RAID1 configuration.
>>>
>>> I read your thread named "SAS 6/iR write performance depends on 
>>> kernel version, blade server m600". BTW, there are other threads in 
>>> the lists say that Debian (any version) is not going to work on such 
>>> controller. 
>>>       
>> We are all using linux, we should not say debian won't .. or redhat 
>> will.. What we like about debian is the packaging system and the very 
>> few packages installed at first which is perfect for servers.
>> Debian Etch is working prefectly on LSI sas 6. That's a kernel issue. 
>> Fortunatly all the "Dell supported distrib" are using a kernel <2.6.18.
>>     
>
> Now I understand. If I'm correct, we should simply compile a kernel 
> version less than 2.6.18 and everything should be fine.
>
>   
>> I'm still looking at kernel patch to see why sas 6  LSI controller is 
>> working so bad in the last kernels. I'm sure now, that the last 
>> kernels are asking firware, and the default settings are bad.
>>
>> What we can say, is that last Ubuntu server 8.04  behaves very badly 
>> with LSI sas 6 (2.6.24)
>>     
>
> Thanks for your feedback.
>
> --
> Alessandro
>
>
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