Re: default file system, was: Comparison to Workstation Technical Specification

[Chris Murphy]

On Feb 26, 2014, at 8:13 AM, Michael Cronenworth <mike(a)cchtml.com&gt; wrote:
>  Ext4 has its btrfs conversion tool. Changing from ext4 to XFS, for
> arguably negligible benefits for Workstations, will make it more difficult for Fedora
> users to transition to btrfs. 
It's an unlikely path because a.) by default we put ext4 on LVM; b.) the convert tool
uses ext4 block size to set btrfs leaf size; c.) the convert tool doesn't set extref,
although it easily could. The last two are a cake walk to change compared to the first.


On Feb 26, 2014, at 8:20 AM, Josh Boyer <jwboyer(a)fedoraproject.org&gt; wrote:

>  I agree switching from ext4 to XFS is likely not worthwhile. 
Whether Server WG goes with ext4 or XFS on LVM, it's worthwhile for Workstation WG to
mimic it merely due to simplicity because then we don't need separate installers or
composes.



On Feb 26, 2014, at 8:24 AM, David Cantrell <dcantrell(a)redhat.com&gt; wrote:
>  
>  I think filesystem variance across different Fedoras really impacts QA more
>  than us.  We already support a lot of filesystems, but the real hit is the
>  QA test matrix. 
QA already tests the file system layouts being discussed. Perhaps the least tested is XFS
on LVM only because the XFS test case doesn't specify LVM, so testers probably split
and do some plain partition and some on LVM. 

If Server WG decides on XFS, it effectively increases the Automatic/Guided/easy/default
installer path's "Partition Scheme" pop-up from four to five options, and
that is a problem. Adamw and I are working on a proposal to reduce these options to one or
two: i.e. a WG chosen product specific default, and maybe "one other" which is
decided by Base WG or FESCo.



Chris Murphy

default file system, was: Comparison to Workstation Technical Specification

[Adam Williamson]

On Wed, 2014-02-26 at 12:18 -0700, Chris Murphy wrote:

>  > I agree switching from ext4 to XFS is likely not worthwhile.
>  
>  Whether Server WG goes with ext4 or XFS on LVM, it's worthwhile for
>  Workstation WG to mimic it merely due to simplicity because then we
>  don't need separate installers or composes. 
I'm broadly in agreement with Chris here. I don't see that any 'plain
partition' filesystem has such a huge difference to the other that it
makes much sense for us to have two products using 'plain partition'
filesystems, by default, but *different* ones.

Choosing btrfs by default is a controversial option, but it's at least
clearly one with very different results from picking a 'plain partition'
filesystem (whether backed by LVM or not). I don't really see the point
in having ext4 for one and xfs for the other. If the only argument for
desktop to keep ext4 if server goes xfs is 'btrfs conversion!', I'm with
cmurf that that's not a compelling argument at all.

The elephant in the room here seems to be LVM backing, I don't see
anyone discussing that. Do desktop and server want to keep LVM backing
by default if they don't go with btrfs? Do desktop and server have
*differing* perspectives there? (Do we want to re-run the Fedora 18 tape
where we switch to no LVM backing by default and then have to go back to
LVM by default for some reason I've forgotten?)
-- 
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Twitter: AdamW_Fedora | XMPP: adamw AT happyassassin . net
http://www.happyassassin.net

default file system, was: Comparison to Workstation Technical Specification

[Stephen Gallagher]

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On 02/26/2014 02:42 PM, Adam Williamson wrote:
>  On Wed, 2014-02-26 at 12:18 -0700, Chris Murphy wrote:
>  
> >> I agree switching from ext4 to XFS is likely not worthwhile.
> > 
> > Whether Server WG goes with ext4 or XFS on LVM, it's worthwhile
> > for Workstation WG to mimic it merely due to simplicity because
> > then we don't need separate installers or composes.
>  
>  I'm broadly in agreement with Chris here. I don't see that any
>  'plain partition' filesystem has such a huge difference to the
>  other that it makes much sense for us to have two products using
>  'plain partition' filesystems, by default, but *different* ones.
>  
>  Choosing btrfs by default is a controversial option, but it's at
>  least clearly one with very different results from picking a 'plain
>  partition' filesystem (whether backed by LVM or not). I don't
>  really see the point in having ext4 for one and xfs for the other.
>  If the only argument for desktop to keep ext4 if server goes xfs is
>  'btrfs conversion!', I'm with cmurf that that's not a compelling
>  argument at all.
>  
>  The elephant in the room here seems to be LVM backing, I don't see 
>  anyone discussing that. Do desktop and server want to keep LVM
>  backing by default if they don't go with btrfs? Do desktop and
>  server have *differing* perspectives there? (Do we want to re-run
>  the Fedora 18 tape where we switch to no LVM backing by default and
>  then have to go back to LVM by default for some reason I've
>  forgotten?)
>   
I can only speak for myself, but regardless of whether Server picks
ext4 or XFS, I think we definitely want it to be on LVM. (LVM
thin-provisioning is another can of worms, but let's talk about that
separately).
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default file system, was: Comparison to Workstation Technical Specification

[Simo Sorce]

On Wed, 2014-02-26 at 11:42 -0800, Adam Williamson wrote:
>  The elephant in the room here seems to be LVM backing, I don't
> see
>  anyone discussing that. Do desktop and server want to keep LVM backing
>  by default if they don't go with btrfs? Do desktop and server have
>  *differing* perspectives there? (Do we want to re-run the Fedora 18 tape
>  where we switch to no LVM backing by default and then have to go back to
>  LVM by default for some reason I've forgotten?) 
I can only speak from personal experience here, but I always use LVM on
servers and that has served me extremely well. I also always use XFS for
servers on which I store data.

LVM has been fundamental many times to be able to add more disks to my
server w/o long downtime, and even replacing disks with bigger ones
again w/o (or reduced) downtime.

I think this is a pretty important feature for a Server OS.

Copying TBs of data can take quite some time, and being forced to do
that while keeping the server offline because there is no LVM layer to
automatically move all the blocks really sucks.

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York

default file system, was: Comparison to Workstation Technical Specification

[Josh Boyer]

On Wed, Feb 26, 2014 at 2:42 PM, Adam Williamson <awilliam(a)redhat.com&gt; wrote:
>  On Wed, 2014-02-26 at 12:18 -0700, Chris Murphy wrote:
>
> > > I agree switching from ext4 to XFS is likely not worthwhile.
> >
> > Whether Server WG goes with ext4 or XFS on LVM, it's worthwhile for
> > Workstation WG to mimic it merely due to simplicity because then we
> > don't need separate installers or composes.
>
>  I'm broadly in agreement with Chris here. I don't see that any 'plain
>  partition' filesystem has such a huge difference to the other that it
>  makes much sense for us to have two products using 'plain partition'
>  filesystems, by default, but *different* ones. 
So my answer was primarily under the premise of Workstation alone.  If
Server switches to XFS, then yeah maybe using XFS on Workstation makes
more sense.  If Server doesn't, then there's really no benefit to
Workstation doing that.  I think we're in violent agreement on this,
so we can stop emailing about it now.

>  The elephant in the room here seems to be LVM backing, I don't
> see
>  anyone discussing that. Do desktop and server want to keep LVM backing
>  by default if they don't go with btrfs? Do desktop and server have
>  *differing* perspectives there? (Do we want to re-run the Fedora 18 tape
>  where we switch to no LVM backing by default and then have to go back to
>  LVM by default for some reason I've forgotten?) 
I'm not sure on the Workstation front.  The dm-thinp stuff might be a
solution to some of the snapshotting features btrfs would provide, but
I think that doesn't necessitate LVM thinp.  (IIRC, Alexander Larsson
found raw dm-thinp to be more usable and performant for his Docker
stuff too.)  It's something we'll have to take up within the WG.

josh