Disable cache disk

Disable cache disk

[Yves Crespin]

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Hello,

I write a lot of files on a USB disk for video monitoring archiving.
The write program is faster than the USB.
Cache disk take all RAM and kernel start swapping and everything become 
very slow.
1/ is-it possible to *really* be synchronize. I prefer to have a blocked 
write() than use cache and get swap!
2/ is-it possible to disable cache disk ?

Thanks,

 Yves

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Re: Disable cache disk

[Michael Tokarev]

Yves Crespin wrote:
> Hello,
> 
> I write a lot of files on a USB disk for video monitoring archiving.
> The write program is faster than the USB.
> Cache disk take all RAM and kernel start swapping and everything become 
> very slow.
> 1/ is-it possible to *really* be synchronize. I prefer to have a blocked 
> write() than use cache and get swap!
> 2/ is-it possible to disable cache disk ?

Try open() with O_DIRECT flag for a start.

/mjt

Re: Disable cache disk

[Christian Bornträger]

On Wednesday 30 March 2005 15:00, Yves Crespin wrote:
> 1/ is-it possible to *really* be synchronize. I prefer to have a blocked
> write() than use cache and get swap!

Try to mount with the sync option. 

> 2/ is-it possible to disable cache disk ?

your copy tool has to support/use O_DIRECT

Re: Disable cache disk

[Yves Crespin]

Christian Bornträger wrote:

>On Wednesday 30 March 2005 15:00, Yves Crespin wrote:
>  
>
>>1/ is-it possible to *really* be synchronize. I prefer to have a blocked
>>write() than use cache and get swap!
>>    
>>
>
>Try to mount with the sync option. 
>  
>
exactly async and noatime ?

>  
>
>>2/ is-it possible to disable cache disk ?
>>    
>>
>
>your copy tool has to support/use O_DIRECT
>  
>
is O_DIRECT a POSIX option ?
http://www.opengroup.org/onlinepubs/007908799/xsh/open.html
Is O_SYNC also necessary ?

Re: Disable cache disk

[Christian Borntraeger]

Yves Crespin wrote:
> Christian Bornträger wrote:
> >On Wednesday 30 March 2005 15:00, Yves Crespin wrote:
> >>1/ is-it possible to *really* be synchronize. I prefer to have a
> >> blocked write() than use cache and get swap!
> >Try to mount with the sync option.
> exactly async and noatime ?

No.  async is exactly the behaviour you dont want. Problem is, the "sync" 
mount option is not available for every file system. At least ext2, ext3, 
and ufs support this option. No idea about other filesystems.


> >>2/ is-it possible to disable cache disk ?
> >
> >your copy tool has to support/use O_DIRECT
>
> is O_DIRECT a POSIX option ?

No it is a Linux extension.