XFS syncs

XFS syncs

[flux]

Hi,

I issue 'mkdir abc' on my xfs partition the cut off the power. After 
reboot there's no 'abc' directoy. However, when I do that on ext4 the 
'abc' direcory is always created after reboots. All the settings, about 
mount options are default for my distro. What am I missing or how do I 
change the things of the jounral or whatever?

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Re: XFS syncs

[Stan Hoeppner]

On 7/3/2014 1:05 PM, flux@hotbox.ru wrote:
> Hi,
> 
> I issue 'mkdir abc' on my xfs partition the cut off the power. After
> reboot there's no 'abc' directoy. However, when I do that on ext4 the
> 'abc' direcory is always created after reboots. All the settings, about
> mount options are default for my distro. What am I missing or how do I
> change the things of the jounral or whatever?

So, you want XFS to behave like EXT4, is this correct?  Do you have an
actual workload where you need to cut power immediately after issuing
commands, as described above?

Cheers,

Stan

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Re: XFS syncs

[Dave Chinner]

On Thu, Jul 03, 2014 at 10:05:53PM +0400, flux@hotbox.ru wrote:
> Hi,
> 
> I issue 'mkdir abc' on my xfs partition the cut off the power. After
> reboot there's no 'abc' directoy.

Because you didn't sync(1) the filesystem or fsync(2) the directory
before you cut the power. Hence the change never hit the disk.

> However, when I do that on ext4
> the 'abc' direcory is always created after reboots.

That'll be pure fluke - ext4 delays journal writes on namespace
operations just like XFS does.

> All the
> settings, about mount options are default for my distro. What am I
> missing or how do I change the things of the jounral or whatever?

If you want directory operations to hitthe disk immediately, then
mount with the "-o wsync" option. Be aware, however, that this will
kill performance unless you have expensive storage with a large
amount of battery backed write cache in front of the disks. There's
a good chance it will also cause excessive wear on SSDs due to the
frequent journal writes.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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Re: XFS syncs

[flux]

Hello Dave,

Thanks for the explanation and your suggestion to use wsync option.

On 07/04/2014 03:17 AM, Dave Chinner wrote:
> On Thu, Jul 03, 2014 at 10:05:53PM +0400, flux@hotbox.ru wrote:
>> Hi,
>>
>> I issue 'mkdir abc' on my xfs partition the cut off the power. After
>> reboot there's no 'abc' directoy.
>
> Because you didn't sync(1) the filesystem or fsync(2) the directory
> before you cut the power. Hence the change never hit the disk.
>
>> However, when I do that on ext4
>> the 'abc' direcory is always created after reboots.
>
> That'll be pure fluke - ext4 delays journal writes on namespace
> operations just like XFS does.
>
>> All the
>> settings, about mount options are default for my distro. What am I
>> missing or how do I change the things of the jounral or whatever?
>
> If you want directory operations to hitthe disk immediately, then
> mount with the "-o wsync" option. Be aware, however, that this will
> kill performance unless you have expensive storage with a large
> amount of battery backed write cache in front of the disks. There's
> a good chance it will also cause excessive wear on SSDs due to the
> frequent journal writes.
>
> Cheers,
>
> Dave.
>

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