Btrfs devel - Nov 2010 - Btrfs-progs: Update man page for mixed data+metadata option.

Update the mkfs.btrfs man page for the -M option to mix data and
metadata chunks.

Signed-off-by: Mitch Harder <mitch.harder@sabayonlinux.org>
---
 man/mkfs.btrfs.8.in |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
index 1e14c6c..c23dddc 100644
--- a/man/mkfs.btrfs.8.in
+++ b/man/mkfs.btrfs.8.in
@@ -9,6 +9,7 @@ mkfs.btrfs \- create an btrfs filesystem
 [ \fB \-l\fP\fI leafsize\fP ]
 [ \fB \-L\fP\fI label\fP ]
 [ \fB \-m\fP\fI metadata profile\fP ]
+[ \fB \-M\fP\fI mixed data+metadata\fP ]
 [ \fB \-n\fP\fI nodesize\fP ]
 [ \fB \-s\fP\fI sectorsize\fP ]
 [ \fB \-h\fP ]
@@ -45,6 +46,10 @@ Specify a label for the filesystem.
 Specify how metadata must be spanned across the devices specified. Valid
 values are raid0, raid1, raid10 or single.
 .TP
+\fB\-M\fR, \fB\-\-mixed\fR
+Mix data and metadata chunks together for more efficient space 
+utilization.
+.TP
 \fB\-n\fR, \fB\-\-nodesize \fIsize\fR
 Specify the nodesize. By default the value is set to the pagesize.
 .TP
-- 
1.7.2.2

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On Wed, Nov 10, 2010 at 12:02:18PM -0600, Mitch Harder
wrote:
> Update the mkfs.btrfs man page for the -M option to mix data and
> metadata chunks.
> 
> Signed-off-by: Mitch Harder <mitch.harder@sabayonlinux.org>
> ---
>  man/mkfs.btrfs.8.in |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
> index 1e14c6c..c23dddc 100644
> --- a/man/mkfs.btrfs.8.in
> +++ b/man/mkfs.btrfs.8.in
> @@ -9,6 +9,7 @@ mkfs.btrfs \- create an btrfs filesystem
>  [ \fB \-l\fP\fI leafsize\fP ]
>  [ \fB \-L\fP\fI label\fP ]
>  [ \fB \-m\fP\fI metadata profile\fP ]
> +[ \fB \-M\fP\fI mixed data+metadata\fP ]
>  [ \fB \-n\fP\fI nodesize\fP ]
>  [ \fB \-s\fP\fI sectorsize\fP ]
>  [ \fB \-h\fP ]
> @@ -45,6 +46,10 @@ Specify a label for the filesystem.
>  Specify how metadata must be spanned across the devices specified. Valid
>  values are raid0, raid1, raid10 or single.
>  .TP
> +\fB\-M\fR, \fB\-\-mixed\fR
> +Mix data and metadata chunks together for more efficient space 
> +utilization.
> +.TP
>  \fB\-n\fR, \fB\-\-nodesize \fIsize\fR
>  Specify the nodesize. By default the value is set to the pagesize.
>  .TP
> -- 
> 1.7.2.2
Let''s mention that it''s for smaller filesystems since it has a
significant
performance impact when using mixed block groups on larger filesystems.  Thanks,

Josef
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On Wed, Nov 10, 2010 at 8:10 PM, Josef Bacik <josef@redhat.com>
wrote:
> On Wed, Nov 10, 2010 at 12:02:18PM -0600, Mitch Harder wrote:
>> Update the mkfs.btrfs man page for the -M option to mix data and
>> metadata chunks.
>>
>> Signed-off-by: Mitch Harder <mitch.harder@sabayonlinux.org>
>> ---
>>  man/mkfs.btrfs.8.in |    5 +++++
>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
>> index 1e14c6c..c23dddc 100644
>> --- a/man/mkfs.btrfs.8.in
>> +++ b/man/mkfs.btrfs.8.in
>> @@ -9,6 +9,7 @@ mkfs.btrfs \- create an btrfs filesystem
>>  [ \fB \-l\fP\fI leafsize\fP ]
>>  [ \fB \-L\fP\fI label\fP ]
>>  [ \fB \-m\fP\fI metadata profile\fP ]
>> +[ \fB \-M\fP\fI mixed data+metadata\fP ]
>>  [ \fB \-n\fP\fI nodesize\fP ]
>>  [ \fB \-s\fP\fI sectorsize\fP ]
>>  [ \fB \-h\fP ]
>> @@ -45,6 +46,10 @@ Specify a label for the filesystem.
>>  Specify how metadata must be spanned across the devices specified.
Valid
>>  values are raid0, raid1, raid10 or single.
>>  .TP
>> +\fB\-M\fR, \fB\-\-mixed\fR
>> +Mix data and metadata chunks together for more efficient space
>> +utilization.
>> +.TP
>>  \fB\-n\fR, \fB\-\-nodesize \fIsize\fR
>>  Specify the nodesize. By default the value is set to the pagesize.
>>  .TP
>> --
>> 1.7.2.2
>
> Let''s mention that it''s for smaller filesystems since it
has a significant
> performance impact when using mixed block groups on larger filesystems.
 Thanks,
>
> Josef
>
OK, how about:

Mix data and metadata chunks together for more efficient space
utilization, especially on smaller file systems.  Incurs a performance
penalty.
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On Wed, Nov 10, 2010 at 9:53 PM, Mitch Harder
<mitch.harder@sabayonlinux.org> wrote:
> On Wed, Nov 10, 2010 at 8:10 PM, Josef Bacik <josef@redhat.com>
wrote:
>> On Wed, Nov 10, 2010 at 12:02:18PM -0600, Mitch Harder wrote:
>>> Update the mkfs.btrfs man page for the -M option to mix data and
>>> metadata chunks.
>>>
>>> Signed-off-by: Mitch Harder <mitch.harder@sabayonlinux.org>
>>> ---
>>>  man/mkfs.btrfs.8.in |    5 +++++
>>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
>>> index 1e14c6c..c23dddc 100644
>>> --- a/man/mkfs.btrfs.8.in
>>> +++ b/man/mkfs.btrfs.8.in
>>> @@ -9,6 +9,7 @@ mkfs.btrfs \- create an btrfs filesystem
>>>  [ \fB \-l\fP\fI leafsize\fP ]
>>>  [ \fB \-L\fP\fI label\fP ]
>>>  [ \fB \-m\fP\fI metadata profile\fP ]
>>> +[ \fB \-M\fP\fI mixed data+metadata\fP ]
>>>  [ \fB \-n\fP\fI nodesize\fP ]
>>>  [ \fB \-s\fP\fI sectorsize\fP ]
>>>  [ \fB \-h\fP ]
>>> @@ -45,6 +46,10 @@ Specify a label for the filesystem.
>>>  Specify how metadata must be spanned across the devices specified.
Valid
>>>  values are raid0, raid1, raid10 or single.
>>>  .TP
>>> +\fB\-M\fR, \fB\-\-mixed\fR
>>> +Mix data and metadata chunks together for more efficient space
>>> +utilization.
>>> +.TP
>>>  \fB\-n\fR, \fB\-\-nodesize \fIsize\fR
>>>  Specify the nodesize. By default the value is set to the pagesize.
>>>  .TP
>>> --
>>> 1.7.2.2
>>
>> Let''s mention that it''s for smaller filesystems since
it has a significant
>> performance impact when using mixed block groups on larger filesystems.
 Thanks,
>>
>> Josef
>>
>
> OK, how about:
>
> Mix data and metadata chunks together for more efficient space
> utilization, especially on smaller file systems.  Incurs a performance
> penalty.
in a previous message, Josef had mentioned it was specifically for
<1GB _only_...

if so, wording should probably make it perfectly clear that the option
is totally inappropriate for _anybody_ unless you meet
specific/special criteria.

something like DANGER DANGER WILL ROBINSON :-) unless i''m mistaken of
course.

C Anthony
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On Wed, Nov 10, 2010 at 09:53:23PM -0600, Mitch Harder
wrote:
> On Wed, Nov 10, 2010 at 8:10 PM, Josef Bacik <josef@redhat.com>
wrote:
> > On Wed, Nov 10, 2010 at 12:02:18PM -0600, Mitch Harder wrote:
> >> Update the mkfs.btrfs man page for the -M option to mix data and
> >> metadata chunks.
> >>
> >> Signed-off-by: Mitch Harder <mitch.harder@sabayonlinux.org>
> >> ---
> >>  man/mkfs.btrfs.8.in |    5 +++++
> >>  1 files changed, 5 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
> >> index 1e14c6c..c23dddc 100644
> >> --- a/man/mkfs.btrfs.8.in
> >> +++ b/man/mkfs.btrfs.8.in
> >> @@ -9,6 +9,7 @@ mkfs.btrfs \- create an btrfs filesystem
> >>  [ \fB \-l\fP\fI leafsize\fP ]
> >>  [ \fB \-L\fP\fI label\fP ]
> >>  [ \fB \-m\fP\fI metadata profile\fP ]
> >> +[ \fB \-M\fP\fI mixed data+metadata\fP ]
> >>  [ \fB \-n\fP\fI nodesize\fP ]
> >>  [ \fB \-s\fP\fI sectorsize\fP ]
> >>  [ \fB \-h\fP ]
> >> @@ -45,6 +46,10 @@ Specify a label for the filesystem.
> >>  Specify how metadata must be spanned across the devices
specified. Valid
> >>  values are raid0, raid1, raid10 or single.
> >>  .TP
> >> +\fB\-M\fR, \fB\-\-mixed\fR
> >> +Mix data and metadata chunks together for more efficient space
> >> +utilization.
> >> +.TP
> >>  \fB\-n\fR, \fB\-\-nodesize \fIsize\fR
> >>  Specify the nodesize. By default the value is set to the
pagesize.
> >>  .TP
> >> --
> >> 1.7.2.2
> >
> > Let''s mention that it''s for smaller filesystems
since it has a significant
> > performance impact when using mixed block groups on larger
filesystems.  Thanks,
> >
> > Josef
> >
> 
> OK, how about:
> 
> Mix data and metadata chunks together for more efficient space
> utilization, especially on smaller file systems.  Incurs a performance
> penalty.
Let''s say

This feature incurs a performance penalty in larger filesystems, it is
recommended for use with filesystems of 1 GiB or smaller.

Thanks,

Josef
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On 11/11/10 23:52, Josef Bacik wrote:
> This feature incurs a performance penalty in larger filesystems, it is
> recommended for use with filesystems of 1 GiB or smaller.
Maybe slightly stronger, for example:

This feature incurs a performance penalty for larger filesystems and it
is ONLY recommended for use with filesystems of 1 GiB or smaller.

Is it worth having a check and a warning printed if a user does
try and make a filesystem larger than 1GiB with this option ?

Just in case they don''t RTFM...

cheers,
Chris
-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC
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On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel
wrote:
> On 11/11/10 23:52, Josef Bacik wrote:
> 
> > This feature incurs a performance penalty in larger filesystems, it is
> > recommended for use with filesystems of 1 GiB or smaller.
> 
> Maybe slightly stronger, for example:
> 
> This feature incurs a performance penalty for larger filesystems and it
> is ONLY recommended for use with filesystems of 1 GiB or smaller.
> 
> Is it worth having a check and a warning printed if a user does
> try and make a filesystem larger than 1GiB with this option ?
> 
> Just in case they don''t RTFM...
>
No because depending on your usage it''s actually kind of usefull for
anything
less than 5 GiB, and you''re only looking at about a 5-10% perf
degredation when
using it on larger filesystems.  Thanks,

Josef 
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On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik <josef@redhat.com>
wrote:
> On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote:
>> On 11/11/10 23:52, Josef Bacik wrote:
>>
>> > This feature incurs a performance penalty in larger filesystems,
it is
>> > recommended for use with filesystems of 1 GiB or smaller.
>>
>> Maybe slightly stronger, for example:
>>
>> This feature incurs a performance penalty for larger filesystems and it
>> is ONLY recommended for use with filesystems of 1 GiB or smaller.
>>
>> Is it worth having a check and a warning printed if a user does
>> try and make a filesystem larger than 1GiB with this option ?
>>
>> Just in case they don''t RTFM...
>>
>
> No because depending on your usage it''s actually kind of usefull
for anything
> less than 5 GiB, and you''re only looking at about a 5-10% perf
degredation when
> using it on larger filesystems.  Thanks,
>
Then a warning of 10% slowdown if > 10GB would be good.  It''s
surprising how many will just read some forum post and not concern
themselves with the docs at all.

And making them type "yes" if > 100GB is probably a good idea
too...
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On Friday 12 of November 2010 18:44:12 you wrote:
> On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik <josef@redhat.com>
wrote:
> > On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote:
> >> On 11/11/10 23:52, Josef Bacik wrote:
> >> > This feature incurs a performance penalty in larger
filesystems, it is
> >> > recommended for use with filesystems of 1 GiB or smaller.
> >> 
> >> Maybe slightly stronger, for example:
> >> 
> >> This feature incurs a performance penalty for larger filesystems
and it
> >> is ONLY recommended for use with filesystems of 1 GiB or smaller.
> >> 
> >> Is it worth having a check and a warning printed if a user does
> >> try and make a filesystem larger than 1GiB with this option ?
> >> 
> >> Just in case they don''t RTFM...
> > 
> > No because depending on your usage it''s actually kind of
usefull for
> > anything less than 5 GiB, and you''re only looking at about a
5-10% perf
> > degredation when using it on larger filesystems.  Thanks,
> 
> Then a warning of 10% slowdown if > 10GB would be good.  It''s
> surprising how many will just read some forum post and not concern
> themselves with the docs at all.
> 
> And making them type "yes" if > 100GB is probably a good idea
too...
My 2c: I''m against bloating the program just because of people who
don''t RTFM.
Just mention it clearly in docs and that''s enough, linux does what
it''s asked
for, not the "Are you really really sure you want to do this?" known
from some
other OS. Anyway, btrfs-progs would be probably run by a user with root 
privileges and such should be aware of what actions they do, or read the man 
page. My opinion. 
Cheers, Mark

-- 

Marek Otahal :o)
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On Fri, Nov 12, 2010 at 4:44 AM, Mike Fedyk <mfedyk@mikefedyk.com>
wrote:
> On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik <josef@redhat.com>
wrote:
>> On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote:
>>> On 11/11/10 23:52, Josef Bacik wrote:
>>>
>>> > This feature incurs a performance penalty in larger
filesystems, it is
>>> > recommended for use with filesystems of 1 GiB or smaller.
>>>
>>> Maybe slightly stronger, for example:
>>>
>>> This feature incurs a performance penalty for larger filesystems
and it
>>> is ONLY recommended for use with filesystems of 1 GiB or smaller.
>>>
>>> Is it worth having a check and a warning printed if a user does
>>> try and make a filesystem larger than 1GiB with this option ?
>>>
>>> Just in case they don''t RTFM...
>>>
>>
>> No because depending on your usage it''s actually kind of
usefull for anything
>> less than 5 GiB, and you''re only looking at about a 5-10% perf
degredation when
>> using it on larger filesystems.  Thanks,
>>
>
> Then a warning of 10% slowdown if > 10GB would be good.  It''s
> surprising how many will just read some forum post and not concern
> themselves with the docs at all.
>
> And making them type "yes" if > 100GB is probably a good idea
too...
>
Just for clarification, you''ll probably see a ~5-10% slowdown for any
size partition, not just "if > 10 GB"

But for smaller filesystems (~<5 GiB), you may want to accept the
performance penalty for more efficient disk space utilization.

For really small filesystems (~<1 GiB), using Btrfs defaults can
really start to impact on space utilization.  So the parent
data+metadata patch currently forces the data+metadata option on <1
GiB.

The Wiki is probably a better place for more extensive discussion of
the merits and trade-offs of this option.

The user still needs to actively "opt-in" to this option (unless their
partition is < GiB), and the man page will indicate a performance
penalty is incurred.

For something as important as changing your filesystem default
settings, it seems fair to expect the user has done their homework
when changing from the default setting.
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On Fri, Nov 12, 2010 at 6:28 AM, Marek Otahal <markotahal@gmail.com>
wrote:
> On Friday 12 of November 2010 18:44:12 you wrote:
>> On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik <josef@redhat.com>
wrote:
>> > On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote:
>> >> On 11/11/10 23:52, Josef Bacik wrote:
>> >> > This feature incurs a performance penalty in larger
filesystems, it is
>> >> > recommended for use with filesystems of 1 GiB or smaller.
>> >>
>> >> Maybe slightly stronger, for example:
>> >>
>> >> This feature incurs a performance penalty for larger
filesystems and it
>> >> is ONLY recommended for use with filesystems of 1 GiB or
smaller.
>> >>
>> >> Is it worth having a check and a warning printed if a user
does
>> >> try and make a filesystem larger than 1GiB with this option ?
>> >>
>> >> Just in case they don''t RTFM...
>> >
>> > No because depending on your usage it''s actually kind of
usefull for
>> > anything less than 5 GiB, and you''re only looking at
about a 5-10% perf
>> > degredation when using it on larger filesystems.  Thanks,
>>
>> Then a warning of 10% slowdown if > 10GB would be good.
 It''s
>> surprising how many will just read some forum post and not concern
>> themselves with the docs at all.
>>
>> And making them type "yes" if > 100GB is probably a good
idea too...
> My 2c: I''m against bloating the program just because of people who
don''t RTFM.
> Just mention it clearly in docs and that''s enough, linux does what
it''s asked
> for, not the "Are you really really sure you want to do this?"
known from some
> other OS. Anyway, btrfs-progs would be probably run by a user with root
I was thinking of what ssh does when it sees a changed key...
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On Fri, Nov 12, 2010 at 10:56 AM, Mike Fedyk <mfedyk@mikefedyk.com>
wrote:
> On Fri, Nov 12, 2010 at 6:28 AM, Marek Otahal <markotahal@gmail.com>
wrote:
>> On Friday 12 of November 2010 18:44:12 you wrote:
>>> On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik
<josef@redhat.com> wrote:
>>> > On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote:
>>> >> On 11/11/10 23:52, Josef Bacik wrote:
>>> >> > This feature incurs a performance penalty in larger
filesystems, it is
>>> >> > recommended for use with filesystems of 1 GiB or
smaller.
>>> >>
>>> >> Maybe slightly stronger, for example:
>>> >>
>>> >> This feature incurs a performance penalty for larger
filesystems and it
>>> >> is ONLY recommended for use with filesystems of 1 GiB or
smaller.
>>> >>
>>> >> Is it worth having a check and a warning printed if a user
does
>>> >> try and make a filesystem larger than 1GiB with this
option ?
>>> >>
>>> >> Just in case they don''t RTFM...
>>> >
>>> > No because depending on your usage it''s actually kind
of usefull for
>>> > anything less than 5 GiB, and you''re only looking at
about a 5-10% perf
>>> > degredation when using it on larger filesystems.  Thanks,
>>>
>>> Then a warning of 10% slowdown if > 10GB would be good.
 It''s
>>> surprising how many will just read some forum post and not concern
>>> themselves with the docs at all.
>>>
>>> And making them type "yes" if > 100GB is probably a
good idea too...
>> My 2c: I''m against bloating the program just because of people
who don''t RTFM.
>> Just mention it clearly in docs and that''s enough, linux does
what it''s asked
>> for, not the "Are you really really sure you want to do
this?" known from some
>> other OS. Anyway, btrfs-progs would be probably run by a user with root
>
> I was thinking of what ssh does when it sees a changed key...
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>
Thanks for the input everybody.

For now, I''m going to leave the man page entry relatively simple to
stay consistent with the level of information provided by the other
switches.

I''ll submit the updated patch in a fresh post to the M/L.

I see a lot of activity in patch submissions for btrfs-progs, so if
anybody would like me to rework this patch or the parent patch on
implementing data+metadata in btrfs-progs for any reason, let me know.
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