reiserfs and IDE write cache

reiserfs and IDE write cache

[Francisco Javier Cabello]

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Hello,
I have been 'googling' and I have found a lot of people warning about the 
problems with IDE write cache and journaling filesystems. 
Should I disable write cache in my systems using reiserfs3+2.4.25?

I have tried to disable write cache with hdparm (hdparm -W0 /dev/hdc) but it 
is not working  ( you can see write cache is enabled with hdparm 
-i /dev/hdc).
Is there other way to disable write cache?

Regards,

Paco

-- 
One of my most productive days was throwing away 1000 lines of code (Ken 
Thompson)
-----------------
PGP fingerprint: AF69 62B4 97EB F5BB 2C60  B802 568A E122 BBBE 5820
PGP Key available at http://pgp.mit.edu
-----------------


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Re: reiserfs and IDE write cache

[Toby Thain]

On 18-Aug-06, at 3:22 AM, Francisco Javier Cabello wrote:

> Hello,
> I have been 'googling' and I have found a lot of people warning  
> about the
> problems with IDE write cache and journaling filesystems.
> Should I disable write cache in my systems using reiserfs3+2.4.25?
>
> I have tried to disable write cache with hdparm (hdparm -W0 /dev/ 
> hdc) but it
> is not working  ( you can see write cache is enabled with hdparm
> -i /dev/hdc).
> Is there other way to disable write cache?


Get a UPS. :)

Here are some links I collected on this subject a few months ago.


    * _Due to loose interpretations and vendor uniqueness in the ATA  
Standard, there is no defined way that a driver can be assured that  
the disk's cache has been flushed._ (http://developer.apple.com/ 
technotes/tn/tn1040.html)

    * _if write back cache is turned on, it is not difficult to  
create metadata inconsistency or corruption at the file system upon  
power failure._ (http://sr5tech.com/write_back_cache_experiments.htm)

    * Apple forum [[http://lists.apple.com/archives/darwin-dev/2005/ 
Feb/msg00072.html post]] discussing the issues and OS X's F_FULLFSYNC  
feature, which tries hard to flush drive caches.

    * Linux kernel mailing list: _How long can the unwritten data  
linger in the drive cache if the drive is otherwise idle?_ http:// 
lkml.org/lkml/2003/11/2/73

    * Interesting blog [[http://peter-zaitsev.livejournal.com/ 
12639.html?mode=reply post]] on the issue by a !MySQL developer.  
_Transaction will be durable and database intact on the crash only if  
database will perform synchronous IO as synchronous - reporting it is  
done when data is physically on the disk._

    * Detailed [[http://www.opensolaris.org/os/community/arc/caselog/ 
2004/652/ post]] about Open Solaris' approach to the issue (see  
'spec' link)


>
> Regards,
>
> Paco
>
> -- 
> One of my most productive days was throwing away 1000 lines of code  
> (Ken
> Thompson)
> -----------------
> PGP fingerprint: AF69 62B4 97EB F5BB 2C60  B802 568A E122 BBBE 5820
> PGP Key available at http://pgp.mit.edu
> -----------------
>

Re: reiserfs and IDE write cache

[Toby Thain]

On 18-Aug-06, at 3:22 AM, Francisco Javier Cabello wrote:

> Hello,
> I have been 'googling' and I have found a lot of people warning  
> about the
> problems with IDE write cache and journaling filesystems.
> Should I disable write cache in my systems using reiserfs3+2.4.25?
>
> I have tried to disable write cache with hdparm (hdparm -W0 /dev/ 
> hdc) but it
> is not working  ( you can see write cache is enabled with hdparm
> -i /dev/hdc).
> Is there other way to disable write cache?


Get a UPS. :)

Here are some links I collected on this subject a few months ago.


    * _Due to loose interpretations and vendor uniqueness in the ATA  
Standard, there is no defined way that a driver can be assured that  
the disk's cache has been flushed._ (http://developer.apple.com/ 
technotes/tn/tn1040.html)

    * _if write back cache is turned on, it is not difficult to  
create metadata inconsistency or corruption at the file system upon  
power failure._ (http://sr5tech.com/write_back_cache_experiments.htm)

    * Apple forum [[http://lists.apple.com/archives/darwin-dev/2005/ 
Feb/msg00072.html post]] discussing the issues and OS X's F_FULLFSYNC  
feature, which tries hard to flush drive caches.

    * Linux kernel mailing list: _How long can the unwritten data  
linger in the drive cache if the drive is otherwise idle?_ http:// 
lkml.org/lkml/2003/11/2/73

    * Interesting blog [[http://peter-zaitsev.livejournal.com/ 
12639.html?mode=reply post]] on the issue by a !MySQL developer.  
_Transaction will be durable and database intact on the crash only if  
database will perform synchronous IO as synchronous - reporting it is  
done when data is physically on the disk._

    * Detailed [[http://www.opensolaris.org/os/community/arc/caselog/ 
2004/652/ post]] about Open Solaris' approach to the issue (see  
'spec' link)


>
> Regards,
>
> Paco
>
> -- 
> One of my most productive days was throwing away 1000 lines of code  
> (Ken
> Thompson)
> -----------------
> PGP fingerprint: AF69 62B4 97EB F5BB 2C60  B802 568A E122 BBBE 5820
> PGP Key available at http://pgp.mit.edu
> -----------------
>

Re: reiserfs and IDE write cache

[David Masover]

Francisco Javier Cabello wrote:
> Hello,
> I have been 'googling' and I have found a lot of people warning about the 
> problems with IDE write cache and journaling filesystems. 

These problems exist with ANY filesystem, journaling or not.  They also 
exist with no filesystem at all.

> Should I disable write cache in my systems using reiserfs3+2.4.25?

I'm not sure if it will help.  At least with IDE drives, I often cannot 
get the write cache disabled -- it's as if it ignores hdparm.

So, like Toby says, get a UPS.  Or get a laptop instead, if that makes 
any sense.