Re: Converting ext4 to xfs

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On 10/01/2010 11:00 AM, Kwan Lowe wrote:
> On Fri, Oct 1, 2010 at 2:43 AM, Suvayu Ali<fatkasuvayu+linux@xxxxxxxxx>  wrote:
>> Hi everyone,
>>
>> I was wondering if there was any way I could convert an ext4 partition
>> into an xfs partition without copying around files onto a separate
>> partition and reformatting. The partition in question is my /home on a
>> volume group of its own.
> I don't have a real answer except perhaps to create a new LVM for XFS
> then slowly migrate files from one LVM/fs to the other.  As you fill
> space on one, shrink the other filesystem to reclaim those LPs back
> into the VG.  It's messy but should work.  AFAIK, there is no in-place
> conversion utility as the two filesystems are quite different.
>
>> I realised, lately I have been dealing with very large files quite
>> often. Ranging from few hundred megs to a gig or two. So I decided to
>> switch to xfs. Do you think its worth the effort?
> Curios about this though -- what sort of performance are you seeing
> with ext4 vs XFS?  I'm running only a few XFS filesystems but I don't
> see a huge performance increase versus ext4.  My workload is typically
> small sound files.
>
>> Also since we are talking about my /home here, there will also be small
>> conf/settings files along with the large files. Do you think that would
>> be disadvantageous somehow? Would it make more sense to shrink my /home
>> and have a separate xfs partition in the created space for the large files?
>>
>> Thanks for any thoughts on this.
>>
>> --
>> Suvayu
>>
>> Open source is the future. It sets us free.
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Hi Kwan,
I had run performance measurement for reading and
writing of multimegabyte files in linux xfs and ext3.
There was absolutely no denying that ext3 outperformed
xfs by a long shot. Unfortunately, I do not recall the exact
numbers.

One thing that is overlooked by a lot of people is that
the linux xfs IS NOT what runs on the big SGI machines.
Many performance features were not ported because the
x86 architecture does not support, for example,  huge pages
(64k page). the SGI 64 bit architecture supports these
large pages, and perhaps even larger. There are several
implementations of the MIPS architecture.
SGI was probably using a much more robust implementation.
Also, high performance xfs requires large amounts of ram
for the btrees that are searched for the exact blocks to access.
Most x86 machines, especially laptops, are poor targets
for such an architecture. So, many of the features were
removed or scaled back to a size that effectively killed
performance on pc's.

Even on Linux x86_64, with 16GB of ram, the xfs is
still a low performance FS as compared with ext3.

Perhaps SGI will embark on a new port for the new intel
64bit architectures (don't hold your breath :)

These tests were done back in 2006.

I am not sure if the linux xfs has undergone
any serious performance improvements since then.

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