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Re: ext3 on Linux software RAID1



On Sat, 2002-03-02 at 09:18, Rechenberg, Andrew wrote:
> Everyone,
> 
> We just had a pretty bad crash on one of production boxes and the ext2
> filesystem on the data partition of our box had some major filesystem
> corruption.  Needless to say, I am now looking into converting the
> filesystem to ext3 and I have some questions regarding ext3 and Linux
> software RAID.

I'm sure you already know this, but ext2 sucks.  :-)

> I have read that previously there were some issues running ext3 on a
> software raid device (/dev/mdN), but that most of those issues are resolved
> by running kernel 2.4.x.  Currently we are running 2.4.16 on our producton
> system and we have a rather complicated hardware/software RAID configuration
> on the box.

Correct, there aren't any bugs that I know of in running ext3 on RAID
under the 2.4.x kernel series.

[snip]

> Now that you know the basics of my system and our ideal requirements, I have
> a few questions:  
> 
> - Is it wise to convert the filesystem on /dev/md1 to ext3? 

I see no reason that converting to ext3 would be a poor choice.  It will
allow you to recover from a hugely higher percentage of crashes.  fscks
are still necessary from time to time, but unlike ext2, they actually
work.

> - Have the issues with ext3 on Linux RAID been resolved?

To the best of my knowledge, yes.

> - Will the failing and resyncing of /dev/md1 happening on a daily basis
> cause problems with the journalling? 

The filesystem sees the Linux software RAID devices as just another
block device, so it shouldn't even know or care about the "failures".

> - Do you think the filesystem would be stable enough for 18x7 availability?

Yes, but if you're using unpatched 2.4.16, I think you've got some
virtual memory issues that need to be resolved.  There are a few people
who have patches to get the VM in the kernel up to "enterprise" levels,
but they're not necessarily in the main kernels yet.  Red Hat 7.2
shipped with ext3 as the default filesystem, which gets it onto a huge
number of machines, some under much higher demand situations than this
one sounds like.

[snip filesystem questions]

I'm not sure, I'm not that much of a filesystem expert.  I expect that
someone else will know much better.
	Greg

-- 
Portland, Oregon, USA.





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