What's wrong with XFS?

What's wrong with XFS?

[Dave N]

Hi,

Can someone enlighten me what the issue is with XFS? I've been hearing a lot of good things on the Net about XFS. How it's lightening fast, how it has features other file systems do not have (like GRIO, real time volumes, allocate on flush, etc), how it scales very well, etc... but what I didn't hear about is how fast XFS screws things up if something wrong happens. Because of the good things I heard about XFS, I too decided to try it out (been using Ext3 or ReiserFS here for most of the time). Now I'm very disappointed in XFS. I live in an area where power outages are common and I do not have an UPS here. I have a few computers all running on XFS and thought that XFS will give me similar data-integrity like Ext3 or ReiserFS. Now, for the past few weeks I've been experiencing "strange behavior" from XFS. One time, I was reading an article on the Net and had only my Firefox browser open. Then we had a power outage for a short period of time, and when I logged in again into
 KDE, I was surprised to find out that all my desktop icons were messed up all over the place. The other time, again power outage, only this time I was working on a small text file. Booted up again only to find out that the file I was working on contained garbage and I had to start all over again. 

I also heard that XFS depends heavily on the application side for its data-integrity. XFS "thinks" that the application will use the proper calls when writing to disk. What???? How is it the task of the application to ensure the safety of your files??? IMO, programs are there to provide the tools to be productive, NOT to ensure the data safety of your files, that's the task of the file system. Even MySQL provides me with better data-integrity here. If I'm doing some database transaction and the power fails, I can be pretty sure that *most* of the time, MySQL will be just fine next time I boot up.

Why oh why such a beautiful file system like XFS is so terrible at data-integrity? Look what Sun Microsystems did with their new ZFS file system... full atomicity, CRC checksumming and other features to ensure data-integrity... why can't XFS have such things?

Thanks for listening to my preaching here guys

Cheers!

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Re: What's wrong with XFS?

[Klaus Strebel]

Dave N schrieb:
> Hi,
> 
> Even MySQL provides me with better data-integrity here. If I'm doing some database transaction and the power fails, I can be pretty sure that *most* of the time, MySQL will be just fine next time I boot up.
Hallo Dave, MySQL is an application which takes care of data-integrity (
which XFS depends on, as you stated yourself ;-) ). XFS takes care of
the filesystem-integrity, to enable your MySQL to find the files it's
caring of it's content-integrity ( as an application, you see ;-) )
> 
> Why oh why such a beautiful file system like XFS is so terrible at data-integrity? Look what Sun Microsystems did with their new ZFS file system... full atomicity, CRC checksumming and other features to ensure data-integrity... why can't XFS have such things?
To mount multi-gigabyte filesystems after some kind of desaster in
minutes, not in hours or days ;-). It's only caring for meta-data, not
the data.

> 
> Thanks for listening to my preaching here guys
> 
> Cheers!


-- 
Mit freundlichen Grüssen / best regards

Klaus Strebel, Dipl.-Inform. (FH), mailto:klaus.strebel@gmx.net

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Re: What's wrong with XFS?

[Chris Wedgwood]

On Mon, Jan 08, 2007 at 05:13:12AM -0800, Dave N wrote:

>  KDE, I was surprised to find out that all my desktop icons were
>  messed up all over the place.

KDE made assumptions which are not only not true on linux but not true
elsewhere either.  Last I checked KDE dealt with the common cases that
were problematic much better now.

>  The other time, again power outage, only this time I was working on
>  a small text file. Booted up again only to find out that the file I
>  was working on contained garbage and I had to start all over again.

The file should not have contained garbage.  Also, if you
open+truncate+write a file it should be flushed very soon after close
these days, the window is fairly small now.

> I also heard that XFS depends heavily on the application side for
> its data-integrity.  XFS "thinks" that the application will use the
> proper calls when writing to disk. What???? How is it the task of
> the application to ensure the safety of your files???

It's always been that way, for many many years, even before Linux
existed.  If you want your applictions to be portable and reliable
then you have to do do it right.

MTAs are a good example of applications which typically get this right
because people case about lost email and the authors typically take
some effort into make sure it's right.

> IMO, programs are there to provide the tools to be productive, NOT
> to ensure the data safety of your files, that's the task of the file
> system. Even MySQL provides me with better data-integrity here.

Does MySQL allow me to read or write 100s of MB/s continuously on
cheap hardware (for not so cheap hardware I could ask 7GB/s).

> Why oh why such a beautiful file system like XFS is so terrible at
> data-integrity?

There is a cost to full data journalling.  Personally even with ext3 I
find the impact of this high enough I don't use it.

> Look what Sun Microsystems did with their new ZFS file
> system... full atomicity, CRC checksumming and other features to
> ensure data-integrity...

You could argue XFS is showing it's age, it's far from a new
filesystem these days.

ZFS is a very different animal to most traditional filesystems.

> why can't XFS have such things?

Because the realities of life sometime collide with what people want
ideally.

Linux can't have ZFS for licensing reasons but you can have Solaris
with ZFS:  http://opensolaris.org/os/downloads/on/

Re: What's wrong with XFS?

[Olaf Fraczyk]

On Mon, 2007-01-08 at 05:13 -0800, Dave N wrote:
> Hi,
> 
> Can someone enlighten me what the issue is with XFS? I've been hearing a lot of good things on the Net about XFS. How it's lightening fast, how it has features other file systems do not have (like GRIO, real time volumes, allocate on flush, etc), how it scales very well, etc... but what I didn't hear about is how fast XFS screws things up if something wrong happens. Because of the good things I heard about XFS, I too decided to try it out (been using Ext3 or ReiserFS here for most of the time). Now I'm very disappointed in XFS. I live in an area where power outages are common and I do not have an UPS here. I have a few computers all running on XFS and thought that XFS will give me similar data-integrity like Ext3 or ReiserFS. Now, for the past few weeks I've been experiencing "strange behavior" from XFS. One time, I was reading an article on the Net and had only my Firefox browser open. Then we had a power outage for a short period of time, and when I logged in again into
>  KDE, I was surprised to find out that all my desktop icons were messed up all over the place. The other time, again power outage, only this time I was working on a small text file. Booted up again only to find out that the file I was working on contained garbage and I had to start all over again. 
> 
> I also heard that XFS depends heavily on the application side for its data-integrity. XFS "thinks" that the application will use the proper calls when writing to disk. What???? How is it the task of the application to ensure the safety of your files??? IMO, programs are there to provide the tools to be productive, NOT to ensure the data safety of your files, that's the task of the file system. Even MySQL provides me with better data-integrity here. If I'm doing some database transaction and the power fails, I can be pretty sure that *most* of the time, MySQL will be just fine next time I boot up.
> 
> Why oh why such a beautiful file system like XFS is so terrible at data-integrity? Look what Sun Microsystems did with their new ZFS file system... full atomicity, CRC checksumming and other features to ensure data-integrity... why can't XFS have such things?
> 
> Thanks for listening to my preaching here guys
> 
> Cheers!
Hi,

It is nothing wrong with XFS - your expectations are wrong.

You expect data to be journaled, but XFS does journal metadata only, not
data. So, the thing that you get is filesystem integrity not data
integrity.
If you want data integrity you need properly written applications and
__it is__ application's job to care about it's data. It is nothing
unusual here.

If you need data journaling then you need another filesystem - eg. ext3.

I suppose that you find all of it in FAQ.

Regards,

Olaf
-- 
Olaf Fraczyk <olaf@navi.pl>
NAVI

Re: What's wrong with XFS?

[Olaf Frączyk]

On Mon, 2007-01-08 at 05:13 -0800, Dave N wrote:
> Hi,
> 
> Can someone enlighten me what the issue is with XFS? I've been hearing a lot of good things on the Net about XFS. How it's lightening fast, how it has features other file systems do not have (like GRIO, real time volumes, allocate on flush, etc), how it scales very well, etc... but what I didn't hear about is how fast XFS screws things up if something wrong happens. Because of the good things I heard about XFS, I too decided to try it out (been using Ext3 or ReiserFS here for most of the time). Now I'm very disappointed in XFS. I live in an area where power outages are common and I do not have an UPS here. I have a few computers all running on XFS and thought that XFS will give me similar data-integrity like Ext3 or ReiserFS. Now, for the past few weeks I've been experiencing "strange behavior" from XFS. One time, I was reading an article on the Net and had only my Firefox browser open. Then we had a power outage for a short period of time, and when I logged in again into
>  KDE, I was surprised to find out that all my desktop icons were messed up all over the place. The other time, again power outage, only this time I was working on a small text file. Booted up again only to find out that the file I was working on contained garbage and I had to start all over again. 
> 
> I also heard that XFS depends heavily on the application side for its data-integrity. XFS "thinks" that the application will use the proper calls when writing to disk. What???? How is it the task of the application to ensure the safety of your files??? IMO, programs are there to provide the tools to be productive, NOT to ensure the data safety of your files, that's the task of the file system. Even MySQL provides me with better data-integrity here. If I'm doing some database transaction and the power fails, I can be pretty sure that *most* of the time, MySQL will be just fine next time I boot up.
> 
> Why oh why such a beautiful file system like XFS is so terrible at data-integrity? Look what Sun Microsystems did with their new ZFS file system... full atomicity, CRC checksumming and other features to ensure data-integrity... why can't XFS have such things?
> 
> Thanks for listening to my preaching here guys
> 
> Cheers!

Hi,

It is nothing wrong with XFS - your expectations are wrong.

You expect data to be journaled, but XFS does journal metadata only, not
data. So, the thing that you get is filesystem integrity not data
integrity.
If you want data integrity you need properly written applications and
__it is__ application's job to care about it's data. It is nothing
unusual here.

If you need data journaling then you need another filesystem - eg. ext3.

I suppose that you find all of it in FAQ.

Regards,

Olaf
-- 
Olaf Frączyk <olaf@cbk.poznan.pl>

Re: What's wrong with XFS?

[Klaus Strebel]

Chris Wedgwood schrieb:
> On Mon, Jan 08, 2007 at 05:13:12AM -0800, Dave N wrote:
> 
>>  KDE, I was surprised to find out that all my desktop icons were
>>  messed up all over the place.
> 
> KDE made assumptions which are not only not true on linux but not true
> elsewhere either.  Last I checked KDE dealt with the common cases that
> were problematic much better now.
> 
>>  The other time, again power outage, only this time I was working on
>>  a small text file. Booted up again only to find out that the file I
>>  was working on contained garbage and I had to start all over again.
> 
> The file should not have contained garbage.  Also, if you
> open+truncate+write a file it should be flushed very soon after close
> these days, the window is fairly small now.
> 
>> I also heard that XFS depends heavily on the application side for
>> its data-integrity.  XFS "thinks" that the application will use the
>> proper calls when writing to disk. What???? How is it the task of
>> the application to ensure the safety of your files???
> 
> It's always been that way, for many many years, even before Linux
> existed.  If you want your applictions to be portable and reliable
> then you have to do do it right.
> 
> MTAs are a good example of applications which typically get this right
> because people case about lost email and the authors typically take
> some effort into make sure it's right.
> 
>> IMO, programs are there to provide the tools to be productive, NOT
>> to ensure the data safety of your files, that's the task of the file
>> system. Even MySQL provides me with better data-integrity here.
> 
> Does MySQL allow me to read or write 100s of MB/s continuously on
> cheap hardware (for not so cheap hardware I could ask 7GB/s).
> 
>> Why oh why such a beautiful file system like XFS is so terrible at
>> data-integrity?
> 
> There is a cost to full data journalling.  Personally even with ext3 I
> find the impact of this high enough I don't use it.
> 
>> Look what Sun Microsystems did with their new ZFS file
>> system... full atomicity, CRC checksumming and other features to
>> ensure data-integrity...
> 
> You could argue XFS is showing it's age, it's far from a new
> filesystem these days.
> 
> ZFS is a very different animal to most traditional filesystems.
> 
>> why can't XFS have such things?
> 
> Because the realities of life sometime collide with what people want
> ideally.
> 
> Linux can't have ZFS for licensing reasons but you can have Solaris
> with ZFS:  http://opensolaris.org/os/downloads/on/
> 
> 
FYI,

just found this <http://developer.berlios.de/projects/zfs-fuse/>

;-)

Klaus

-- 
Mit freundlichen Grüssen / best regards

Klaus Strebel, Dipl.-Inform. (FH), mailto:klaus.strebel@gmx.net

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Re: What's wrong with XFS?

[Joe Bacom]

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The solution to Dave's problem seems obvious to me.  If you care about your 
data and your hardware, buy a UPS with power conditioning, configure Linux to 
show down when the battery gets low and enjoy the peace of mind knowing that 
even if your away from your machine and the power goes off, the system will 
take care of itself.

Joe

On Monday 08 January 2007 08:49, you wrote:
> On Mon, 2007-01-08 at 05:13 -0800, Dave N wrote:
> > Hi,
> >
> > Can someone enlighten me what the issue is with XFS? I've been hearing a
> > lot of good things on the Net about XFS. How it's lightening fast, how it
> > has features other file systems do not have (like GRIO, real time
> > volumes, allocate on flush, etc), how it scales very well, etc... but
> > what I didn't hear about is how fast XFS screws things up if something
> > wrong happens. Because of the good things I heard about XFS, I too
> > decided to try it out (been using Ext3 or ReiserFS here for most of the
> > time). Now I'm very disappointed in XFS. I live in an area where power
> > outages are common and I do not have an UPS here. I have a few computers
> > all running on XFS and thought that XFS will give me similar
> > data-integrity like Ext3 or ReiserFS. Now, for the past few weeks I've
> > been experiencing "strange behavior" from XFS. One time, I was reading an
> > article on the Net and had only my Firefox browser open. Then we had a
> > power outage for a short period of time, and when I logged in again into
> > KDE, I was surprised to find out that all my desktop icons were messed up
> > all over the place. The other time, again power outage, only this time I
> > was working on a small text file. Booted up again only to find out that
> > the file I was working on contained garbage and I had to start all over
> > again.
> >
> > I also heard that XFS depends heavily on the application side for its
> > data-integrity. XFS "thinks" that the application will use the proper
> > calls when writing to disk. What???? How is it the task of the
> > application to ensure the safety of your files??? IMO, programs are there
> > to provide the tools to be productive, NOT to ensure the data safety of
> > your files, that's the task of the file system. Even MySQL provides me
> > with better data-integrity here. If I'm doing some database transaction
> > and the power fails, I can be pretty sure that *most* of the time, MySQL
> > will be just fine next time I boot up.
> >
> > Why oh why such a beautiful file system like XFS is so terrible at
> > data-integrity? Look what Sun Microsystems did with their new ZFS file
> > system... full atomicity, CRC checksumming and other features to ensure
> > data-integrity... why can't XFS have such things?
> >
> > Thanks for listening to my preaching here guys
> >
> > Cheers!
>
> Hi,
>
> It is nothing wrong with XFS - your expectations are wrong.
>
> You expect data to be journaled, but XFS does journal metadata only, not
> data. So, the thing that you get is filesystem integrity not data
> integrity.
> If you want data integrity you need properly written applications and
> __it is__ application's job to care about it's data. It is nothing
> unusual here.
>
> If you need data journaling then you need another filesystem - eg. ext3.
>
> I suppose that you find all of it in FAQ.
>
> Regards,
>
> Olaf

-- 
A Cringester who requested anonymity says when a friend ran 
Microsoft BS (Baseline Security) Analyzer on a XP Pro SP2 machine,
the cumulative size of the patches that were required exceeded 
the size of the original OS.  I'm not surprised.  The volume
of Microsoft BS I've analyzed could fill Bill Gates' house.
Source: Robert X. Cringely, InfoWorld, Sept. 4, 2006, Issue 36

Penguin: Linux version 2.6.16, 8010.09 BogoMips

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