[linux-lvm] LVM, rawio, ext2?

[linux-lvm] LVM, rawio, ext2?

[David Rees]

Hi,

I'd like to create an ext2 filesystem over a raw io device, is this even
possible?  (If not, skip the rest of this message! ;-)

I've searched various archives, and it seems that people are using lvm along
with rawio (and md!) with success, the question I have is "how do I do it?".

Which way is it best to layer the different io management schemes?  For
example, is it possible to put a md or lvm device on top of 1 or more raw io
devices and keep the data from being buffered?  If not, how do I create an
ext2 filesystem on a raw device?  Forcing it didn't work.

Thanks,
Dave

Re: [linux-lvm] LVM, rawio, ext2?

[José Luis Domingo López]

On Thursday, 23 August 2001, at 01:40:12 -0700,
David Rees wrote:

> Hi,
> 
> I'd like to create an ext2 filesystem over a raw io device, is this even
> possible?  (If not, skip the rest of this message! ;-)
> 
Maybe I'm completely wrong (as usual :), but as far as I know you can
either create a filesystem over any block device (e.g. partition, md, LV,
etc.) and use it as usual, or bind a raw device to an existing block
device, and let the application (e.g. Oracle) manage space on the device
as it wants.

Greetings,

-- 
Jos� Luis Domingo L�pez
Linux Registered User #189436     Debian GNU/Linux Potato (P166 64 MB RAM)
 
jdomingo EN internautas PUNTO org  => � Spam ? Atente a las consecuencias
jdomingo AT internautas DOT   org  => Spam at your own risk

Re: [linux-lvm] LVM, rawio, ext2?

[Heinz J . Mauelshagen]

On Thu, Aug 23, 2001 at 08:49:05PM +0000, José Luis Domingo López wrote:
> On Thursday, 23 August 2001, at 01:40:12 -0700,
> David Rees wrote:
> 
> > Hi,
> > 
> > I'd like to create an ext2 filesystem over a raw io device, is this even
> > possible?  (If not, skip the rest of this message! ;-)
> > 
> Maybe I'm completely wrong (as usual :), but as far as I know you can
> either create a filesystem over any block device (e.g. partition, md, LV,
> etc.) and use it as usual, or bind a raw device to an existing block
> device, and let the application (e.g. Oracle) manage space on the device
> as it wants.

Correct.

You can't run a filesystem on a raw device.

> 
> Greetings,
> 
> -- 
> José Luis Domingo López
> Linux Registered User #189436     Debian GNU/Linux Potato (P166 64 MB RAM)
>  
> jdomingo EN internautas PUNTO org  => ¿ Spam ? Atente a las consecuencias
> jdomingo AT internautas DOT   org  => Spam at your own risk
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

-- 

Regards,
Heinz    -- The LVM Guy --

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    Nevertheless it needs not so stupid people to solve them ***

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Re: [linux-lvm] LVM, rawio, ext2?

[David Rees]

On Thu, Aug 23, 2001 at 10:40:34PM +0200, Heinz J . Mauelshagen wrote:
> On Thu, Aug 23, 2001 at 08:49:05PM +0000, Jos� Luis Domingo L�pez wrote:
> > On Thursday, 23 August 2001, at 01:40:12 -0700,
> > David Rees wrote:
> > 
> > > Hi,
> > > 
> > > I'd like to create an ext2 filesystem over a raw io device, is this even
> > > possible?  (If not, skip the rest of this message! ;-)
> > > 
> > Maybe I'm completely wrong (as usual :), but as far as I know you can
> > either create a filesystem over any block device (e.g. partition, md, LV,
> > etc.) and use it as usual, or bind a raw device to an existing block
> > device, and let the application (e.g. Oracle) manage space on the device
> > as it wants.
> 
> Correct.
> 
> You can't run a filesystem on a raw device.

As I suspected.  I thought I had seen an example of it somewhere but I am
mistaken.

Thanks,
Dave

Re: [linux-lvm] LVM, rawio, ext2?

[Dirk Heinrichs]

David Rees wrote:
> 
> Hi,
> 
> I'd like to create an ext2 filesystem over a raw io device, is this even
> possible?  (If not, skip the rest of this message! ;-)
Why do you want to do that?

These are two opposite things. One uses a raw device where an
application has it's own storage layout, like databases.

If you just want to make shure that your files on an ext2 are written
immediately, then mount with sync option.

Bye...

	Dirk
-- 
Dirk Heinrichs		| Tel:	+49 (0)241 413 260
Configuration Manager	| Fax:	+49 (0)241 413 2640
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D-52070 Aachen		| ICQ#:	110037733

Re: [linux-lvm] LVM, rawio, ext2?

[David Rees]

On Fri, Aug 24, 2007 at 11:31:36AM +0200, Dirk Heinrichs wrote:
> David Rees wrote:
> > 
> > Hi,
> > 
> > I'd like to create an ext2 filesystem over a raw io device, is this even
> > possible?  (If not, skip the rest of this message! ;-)
>
> Why do you want to do that?
> 
> These are two opposite things. One uses a raw device where an
> application has it's own storage layout, like databases.
> 
> If you just want to make shure that your files on an ext2 are written
> immediately, then mount with sync option.

Well, the version of Sybase I'm running (11.9.2) does not support Linux raw
partitions.  Sybase 12.5 reportedly does, but I have a number of servers
running 11.9.2 and don't want to upgrade yet.

Sybase 11.9.2 only supports database data put onto filesystems on Linux, so
I was hoping to create a situation where writes to the filesystem would not
be buffered by the operating system since Sybase has it's own buffers. 

Buffering IO to the filesystem also has the nasty side-effect of putting
increased VM pressure on the system and with 2.4.X kernels this leads to
poor performance.  (See the threads on linux-kernel describing huge
slowdowns with Oracle and 2.4.x when moving from 2.2.x).

Until I can validate my applications on Sybase 12.5 using rawio, I was
looking for a way to prevent filesystem IO from being buffered.

If anyone has any ideas, let me know!

Thanks,
Dave

Re: [linux-lvm] LVM, rawio, ext2?

[Nathan Scott]

hi,

On Fri, Aug 24, 2001 at 07:44:56PM -0700, David Rees wrote:
> On Fri, Aug 24, 2007 at 11:31:36AM +0200, Dirk Heinrichs wrote:
> > David Rees wrote:
> > > 
> > > Hi,
> > > 
> > > I'd like to create an ext2 filesystem over a raw io device, is this even
> > > possible?  (If not, skip the rest of this message! ;-)
> >
> > Why do you want to do that?
> > 
> > These are two opposite things. One uses a raw device where an
> > application has it's own storage layout, like databases.
> > 
> > If you just want to make shure that your files on an ext2 are written
> > immediately, then mount with sync option.
> 
> Well, the version of Sybase I'm running (11.9.2) does not support Linux raw
> partitions.  Sybase 12.5 reportedly does, but I have a number of servers
> running 11.9.2 and don't want to upgrade yet.
> 
> Sybase 11.9.2 only supports database data put onto filesystems on Linux, so
> I was hoping to create a situation where writes to the filesystem would not
> be buffered by the operating system since Sybase has it's own buffers. 
> 
> Buffering IO to the filesystem also has the nasty side-effect of putting
> increased VM pressure on the system and with 2.4.X kernels this leads to
> poor performance.  (See the threads on linux-kernel describing huge
> slowdowns with Oracle and 2.4.x when moving from 2.2.x).
> 
> Until I can validate my applications on Sybase 12.5 using rawio, I was
> looking for a way to prevent filesystem IO from being buffered.
> 
> If anyone has any ideas, let me know!
> 

Does Sybase use O_DIRECT? (Direct I/O) - if so, you can use a
filesystem which supports this (like XFS) to achieve what you
describe above.

I understand some database vendors recommend this above raw I/O
because its easier to backup (using filesystem backup tools).

cheers.

-- 
Nathan

Re: [linux-lvm] LVM, rawio, ext2?

[David Rees]

On Sat, Aug 25, 2001 at 01:13:29PM +1000, Nathan Scott wrote:
> hi,
> 
> Does Sybase use O_DIRECT? (Direct I/O) - if so, you can use a
> filesystem which supports this (like XFS) to achieve what you
> describe above.
> 
> I understand some database vendors recommend this above raw I/O
> because its easier to backup (using filesystem backup tools).

Getting off-topic now, but as far as I know, no.  Is it possible to use
chattr or some other tool to force it to open in O_DIRECT mode?

-Dave

Re: [linux-lvm] LVM, rawio, ext2?

[Andreas Dilger]

On Aug 24, 2001  21:41 -0700, David Rees wrote:
> Getting off-topic now, but as far as I know, no.  Is it possible to use
> chattr or some other tool to force it to open in O_DIRECT mode?

You can get per-file synchronous I/O behaviour by using 'chattr +s <file>'.
This is not quite the same as O_DIRECT, because it still buffers the data.

Cheers, Andreas
-- 
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/