SAS 6/iR write performance depends on kernel version, blade server m600
Dominique LALOT
dom.lalot at gmail.com
Mon May 19 09:40:58 CDT 2008
dell at bobich.net a écrit :
> More likely it's down to one of the patches that RH apply that makes
> it work better.
>
> RH put a lot of effort into making sure hardware from major vendors
> works as well as it should with their distro. To expect similar effort
> to go into smaller and less commercial efforts is misguided.
> Conversely, expecting support for more than RH (and possibly, at a
> push, SuSE in some parts of the world) from hardware vendors is a bit
> much to expect considering the amount of effort required.
>
> For the sake of education and diversity, unpack the RH source RPM and
> see just how many patches they roll into the vanilla kernel tree. That
> should give you the idea of just how much vendor effort goes into it.
I would have done it, if the standard debian etch kernel was'nt working,
but it works. Is 2.6.18 a miraculous kernel? I had a look to debian
kernel patches for 2.6.18 and found nothing. What would have been
intersting is to find a >2.6.18 kernel working somewhere. I can't do
that for RH, and debian testing and Ubuntu server 8 failed the tests.
Not sure that the solution went from a packaging patch.
I'm a little bit lazy to test on Suse..
Dominique
>
>
> In general, I only ever use a non vendor supplied kernel when I have
> no choice. Luckily, that doesn't happen very often.
>
> Gordan
>
> On Mon, 19 May 2008, Dominique LALOT wrote:
>
>> 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.
>>
>> I've just done a disk dump like this:
>> debian:~# dd if=/dev/zero of=test.cdrom bs=10k count=60000
>> 60000+0 records in
>> 60000+0 records out
>> 614400000 bytes (614 MB) copied, 1.12691 seconds, 545 MB/s
>>
>> Well not bad? But, etch has no good standard kernel if you have 8GB
>> of RAM and want to run
>> vservers. So I compiled a new kernel
>> 2.6.22.19-vs2.2.0.7
>> I ran the same test, and I fell to 70MB/s !!
>> So I installed kernel from backports, not better...
>>
>> Well, may be have a look to Ubuntu server as Dell (we hope) will
>> support it on our servers.
>> On Ubuntu 8.04 and 2.6.24-16-server same problem slow speed
>>
>> Well: installed redhat AS5 and check:
>> kernel 2.6.18 and performance OK
>>
>> So: Is 2.6.18 a "magic" kernel?
>>
>> On a good kernel (2.6.18)
>> debian:~# uname -a
>> Linux debian 2.6.18-6-vserver-686 #1 SMP Thu Apr 24 10:53:03
>> UTC 2008 i686
>> GNU/Linux
>>
>> SCSI subsystem initialized
>> Fusion MPT base driver 3.04.01
>> Copyright (c) 1999-2005 LSI Logic Corporation
>> Fusion MPT SAS Host driver 3.04.01
>> ACPI: PCI Interrupt 0000:08:00.0[A] -> GSI 16 (level, low) ->
>> IRQ 177
>> mptbase: Initiating ioc0 bringup
>> ioc0: SAS1068E: Capabilities={Initiator}
>> PCI: Setting latency timer of device 0000:08:00.0 to 64
>> scsi0 : ioc0: LSISAS1068E, FwRev=00143000h, Ports=1, MaxQ=511,
>> IRQ=177
>> Vendor: SEAGATE Model: ST9146802SS Rev: S229
>> Type: Direct-Access ANSI SCSI
>> revision: 05
>> Vendor: SEAGATE Model: ST9146802SS Rev: S229
>> Type: Direct-Access ANSI SCSI
>> revision: 05
>> Vendor: Dell Model: VIRTUAL DISK Rev: 1028
>> Type: Direct-Access ANSI SCSI
>> revision: 05
>> SCSI device sda: 285155328 512-byte hdwr sectors (146000 MB)
>> sda: Write Protect is off
>> sda: Mode Sense: 03 00 00 08
>> SCSI device sda: drive cache: write through
>> SCSI device sda: 285155328 512-byte hdwr sectors (146000 MB)
>> sda: Write Protect is off
>> sda: Mode Sense: 03 00 00 08
>> SCSI device sda: drive cache: write through
>> sda: sda1 sda2 < sda5 >
>> sd 0:1:0:0: Attached scsi disk sda
>>
>> On a "bad kernel"
>> root at ubuntu-test:~# dd if=/dev/zero of=test.cdrom bs=10k
>> count=60000
>> 60000+0 records in
>> 60000+0 records out
>> 614400000 bytes (614 MB) copied, 8,39494 s, 73,2 MB/s
>> root at ubuntu-test:~# uname -a
>> Linux ubuntu-test 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00
>> UTC 2008 i686
>> GNU/Linux
>>
>> [ 96.845125] Fusion MPT base driver 3.04.06
>> [ 96.845127] Copyright (c) 1999-2007 LSI Corporation
>> [ 96.850189] Fusion MPT SAS Host driver 3.04.06
>> [ 96.942269] ACPI: PCI Interrupt 0000:00:1d.1[B] -> GSI 20
>> (level, low) -> IRQ
>> 21
>> [ 99.599489] ioc0: LSISAS1068E B3: Capabilities={Initiator}
>> [ 115.985384] sd 4:1:0:0: [sdb] 285155328 512-byte hardware
>> sectors (146000 MB)
>> [ 115.985610] sd 4:1:0:0: [sdb] Write Protect is off
>> [ 115.985613] sd 4:1:0:0: [sdb] Mode Sense: 03 00 00 08
>> [ 115.986031] sd 4:1:0:0: [sdb] Write cache: disabled, read
>> cache: enabled,
>> doesn't support DPO or FUA
>> [ 115.986494] sd 4:1:0:0: [sdb] 285155328 512-byte hardware
>> sectors (146000 MB)
>> [ 115.986721] sd 4:1:0:0: [sdb] Write Protect is off
>> [ 115.986724] sd 4:1:0:0: [sdb] Mode Sense: 03 00 00 08
>> [ 115.987144] sd 4:1:0:0: [sdb] Write cache: disabled, read
>> cache: enabled,
>> doesn't support DPO or FUA
>> [ 115.987148] sdb: sdb1 sdb2 < sdb5 >
>> [ 116.006731] sd 4:1:0:0: [sdb] Attached SCSI disk
>> [ 116.006773] sd 4:1:0:0: Attached scsi generic sg4 type 0
>>
>> What we see is a bad negociation between kernel and BIOS about the
>> device capabilities
>>
>> It's evident that write caching is not enabled on some kernel. Is
>> there a specific patch or
>> kernel parameters (I checked /boot/config files without success)
>>
>> We tried sdparm to change write caching without success too!
>>
>> Any ideas?
>>
>> Thanks
>>
>> Dominique
>>
>>
>>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Linux-PowerEdge mailing list
> Linux-PowerEdge at dell.com
> http://lists.us.dell.com/mailman/listinfo/linux-poweredge
> Please read the FAQ at http://lists.us.dell.com/faq
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.us.dell.com/pipermail/linux-poweredge/attachments/20080519/42ada270/attachment.htm
More information about the Linux-PowerEdge
mailing list