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Re: [linux-lvm] I:LVM Raw Oracle 9i RAC



dd is no good tool to do such performance numbers.
Do you see any degradations in Oracle compared to non-LVM raw devices ?

Regards,
Heinz    -- The LVM Guy --


On Tue, Sep 16, 2003 at 01:30:05PM +0200, Bernat Covacho, Jose Maria wrote:
> Hello, we have a RedHat Avanced Server 2.1 with kernel version 2.4.9-e.12smp and we use lvm version 1.0.3 (yes I know that the latest "one" version is 1.0.7). I think that the version 2 is too much advanced for us. 
>  
> We have a very strange problem with lvm, oracle and raw devices. If we take a logical volume manager and test it with a simple dd we get:
>  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> time dd if=/dev/MKTP/strip32 of=/dev/null bs=512k count=2048 
> 2048+0 registros leídos
> 2048+0 registros escritos
>  
> real    0m13.394s
> user    0m0.000s
> sys     0m6.090s
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  
> Ok, It works fine, we have 1Gbyte in 13 seconds.
>  
> Now we bind this logical volume to a raw device
>  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> raw /dev/MKTP/strip32 /dev/raw/raw15
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  
> and we try with this:
>  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> time dd if=/dev/raw/raw15  of=/dev/null bs=512k count=2048 
> 2048+0 registros leídos
> 2048+0 registros escritos
>  
> real    0m14.828s
> user    0m0.020s
> sys     0m6.180s
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  
> The same time, more or less, all it's ok. 
>  
> Now we want use this raw (raw15) with oracle. We create a oracle tablespace put data into. We can access it through oracle.
>  
> We stop oracle. Now we repeat the same dd:
>  
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> time dd if=/dev/raw/raw15 of=/dev/null bs=512k count=2048
> 2048+0 registros leídos
> 2048+0 registros escritos
>  
> real    0m48.971s
> user    0m0.010s
> sys     0m11.590s
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  
> Now we have 48 seconds, why?, The only one difference is the tablespace creation.
>  
> We try the same process without lvm and we have the same good time in three cases.
>  
> There are some problem with lvm, raw and oracle?
> How can I avoid this?
>  
> Thanks in advanced
>  
>  
>  
>  
>  
> ========================================
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*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
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