Disable journaling

Disable journaling

[Iuri Diniz]

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BACKGOUND:
I'm looking for a filesystem for linux with these features:

* Fast Sequential Read (FSR)
* Optional: copy on write support (COW)

I think that Ext4 and XFS are the best options. (ZFS too, but current ZFS
implementation is not GPL, maybe brtfs when ready).

why do I want this? because I have a SSD.FSQ will reduce the boot time and
COW will reduce writes on the same sector while allowing snapshots

I've found that XFS has a FSQ support (good job)[1], so I it will be very
fast on SSD (random read == sequential read).

FAIK xfs doesn't support COW, it's ok because ext4 doesn't too.

MY PROBLEM:

I know that my SSD drive supports wearing level on hardware, but anyway I
want to reduce unnecessary writes on my device, so I want to disable
journaling on my filesytem.

Maybe, the ext4 (like ext3 does) will support it by doing this:

tune2fs -O ^has_journal /dev/sda1

Is possible to disable journaling on XFS too?

Thanks in advance

[1] http://www.phoronix.com/scan.php?page=article&item=ext4_benchmarks&num=4

-- 
Iuri Diniz
http://iuridiniz.com [Sou um agitador, não um advogado]
http://blog.igdium.com [Linux on Limbo]


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Re: Disable journaling

[Eric Sandeen]

Iuri Diniz wrote:
> BACKGOUND:
> I'm looking for a filesystem for linux with these features:
> 
> * Fast Sequential Read (FSR)
> * Optional: copy on write support (COW)
> 
> I think that Ext4 and XFS are the best options. (ZFS too, but current ZFS
> implementation is not GPL, maybe brtfs when ready).
> 
> why do I want this? because I have a SSD.FSQ will reduce the boot time and
> COW will reduce writes on the same sector while allowing snapshots
> 
> I've found that XFS has a FSQ support (good job)[1], so I it will be very
> fast on SSD (random read == sequential read).
> 
> FAIK xfs doesn't support COW, it's ok because ext4 doesn't too.
> 
> MY PROBLEM:
> 
> I know that my SSD drive supports wearing level on hardware, but anyway I
> want to reduce unnecessary writes on my device, so I want to disable
> journaling on my filesytem.
> 
> Maybe, the ext4 (like ext3 does) will support it by doing this:
> 
> tune2fs -O ^has_journal /dev/sda1
> 
> Is possible to disable journaling on XFS too?

No, it's not right possible today.  There used to be a sort of config
option that disabled journaling ages ago, but it's gone now.  Not sure
it ever worked on Linux.

Ext4 does have an option to disable journaling now, which is
interesting.  If I ever have any time I'd like to see how hard it might
be to allow a mount option to xfs to also make journaling a no-op.

> Thanks in advance
> 
> [1] http://www.phoronix.com/scan.php?page=article&item=ext4_benchmarks&num=4

Fatally flawed article FWIW, their bonnie++ results are comically bad
(you try deleting 8G files on ext3, see if you can do 200 per second)  I
alerted them to the bonnie++ problems, and explained what they had done
wrong in the results parsing, and although they link to my email, they
leave the ridiculous graphs in place.  The iozone results may be better,
but I'd be very inclined to do my own testing rather than use those
results right now.

-Eric

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Re: Disable journaling

[Nathan Scott]

On Mon, 2009-01-26 at 19:46 -0600, Eric Sandeen wrote:
> 
> > Maybe, the ext4 (like ext3 does) will support it by doing this:
> > 
> > tune2fs -O ^has_journal /dev/sda1
> > 
> > Is possible to disable journaling on XFS too?
> 
> No, it's not right possible today.  There used to be a sort of config
> option that disabled journaling ages ago, but it's gone now.  Not sure
> it ever worked on Linux.

It never did - suffered from adding "never-tested" code paths
in critical areas at the top of the journalling layer in XFS.
Alot of the ordering of work, releasing of resources, etc in
metadata I/O depends on work being scheduled at log I/O
completion time, so if you remove the log entirely, it moves
several things around in ways that are tricky to get right.

Its much simpler to just create a ramdisk and house the journal
there, if you don't want the benefits of a journal (which might
sound attractive, right up to the point you actually need them).

cheers.

--
Nathan

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Re: Disable journaling

[Iuri Diniz]

Hello Eric,

On Mon, Jan 26, 2009 at 11:46 PM, Eric Sandeen <sandeen@sandeen.net> wrote:

> > Is possible to disable journaling on XFS too?
>
> No, it's not right possible today.  There used to be a sort of config
> option that disabled journaling ages ago, but it's gone now.  Not sure
> it ever worked on Linux.
>
> Ext4 does have an option to disable journaling now, which is
> interesting.


Thanks for this information.


> If I ever have any time I'd like to see how hard it might
> be to allow a mount option to xfs to also make journaling a no-op.
>

I'm new on filesystems but, is there another useful reason for having XFS
with no journaling?

I know that a journaling filesystem will slightly degrade the write
performance because the extra write operation (the write on journaling).


>
> > Thanks in advance
> >
> > [1]
> http://www.phoronix.com/scan.php?page=article&item=ext4_benchmarks&num=4
>
> Fatally flawed article FWIW, their bonnie++ results are comically bad
> (you try deleting 8G files on ext3, see if you can do 200 per second)  I
> alerted them to the bonnie++ problems, and explained what they had done
> wrong in the results parsing, and although they link to my email, they
> leave the ridiculous graphs in place.  The iozone results may be better,
> but I'd be very inclined to do my own testing rather than use those
> results right now.


But about the sequential read tests, do you think that are ok?


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