LVM, rawio, ext2?
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
Quoted 5 lines · 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! ;-)
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,
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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
Quoted 5 lines · José Luis Domingo López
Quoted 2 lines · David Rees
Hi,
Quoted 8 lines
Quoted 3 lines
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.
Quoted 16 lines
Greetings,
Signature · 12 lines
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 [email protected] http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html
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Regards,
Heinz -- The LVM Guy --
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=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-Quoted 15 lines · Heinz J . Mauelshagen
Quoted 5 lines · Jos� Luis Domingo L�pez
Quoted 2 lines · David Rees
Hi,
Quoted 8 lines
Quoted 3 lines
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.
Quoted 3 lines
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
Quoted 5 lines · 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! ;-)
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
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Dirk Heinrichs | Tel: +49 (0)241 413 260 Configuration Manager | Fax: +49 (0)241 413 2640 QIS Systemhaus GmbH | Mail: [email protected] Jülicher Str. 338b | Web: http://www.qis-systemhaus.de D-52070 Aachen | ICQ#: 110037733
Quoted 7 lines · Dirk Heinrichs
Quoted 5 lines · 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! ;-)
Quoted 7 lines
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
hi,
Quoted 29 lines · David Rees
Quoted 7 lines · Dirk Heinrichs
Quoted 5 lines · 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! ;-)
Quoted 7 lines
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).
Quoted 5 lines
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.
Signature · 1 line
Nathan
Quoted 8 lines · Nathan Scott
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
Quoted 2 lines · David Rees
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_DIRECTmode?
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
Signature · 3 lines
Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/