when/why to use diffferent raid values for btrfs data & metadata?

when/why to use diffferent raid values for btrfs data & metadata?

[mail ignored]

Hi,

Just getting started with btrfs.

I understand that btrfs stores data/metadata in two different tree
structures =96 one for file/directory names, and one for data blocks.

Reading @,

 http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devic=
es
  Use raid10 for both data and metadata
    mkfs.btrfs -m raid10 -d raid10 /dev/sdb /dev/sdc /dev/sdd /dev/sde

and @,

 "Churning Butter(FS): An Interview with Chris Mason"
  http://www.linux-mag.com/id/7329

    CM Today you can do this:
    mkfs.btrfs -m raid1 -d raid10 /dev/sda /dev/sdb /dev/sdc /dev/sdd
And you=92ll get metadata on raid1 and data on raid10. The raid10 will
use all four drives and the raid1 will use two drives at a time. Yes,
btrfs allows you to pick different values for data or metadata.

The fact that I *can* setup data & metadata differently is clear.  But
I'm not at all clear *why* I'd want to, or what the advantages are.
I'd guess it's a balance/combination of performance & resiliency.

Naively "-m raid10 -d raid10" seems to make the most sense -- if i
have it, use it.

Are there any benchmarks, guidelines or recommendations?
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Re: when/why to use diffferent raid values for btrfs data & metadata?

[RK]

try this article "Linux Don't Need No Stinkin' ZFS: BTRFS Intro &
Benchmarks"
http://www.linux-mag.com/id/7308/3/
, there is a benchmark table and speed analysis (very informative), but
all the benchmarks are done with same -m and -d mkfs.btrfs option


mail ignored wrote:
> Hi,
>
> Just getting started with btrfs.
>
> I understand that btrfs stores data/metadata in two different tree
> structures =96 one for file/directory names, and one for data blocks.
>
> Reading @,
>
>  http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Dev=
ices
>   Use raid10 for both data and metadata
>     mkfs.btrfs -m raid10 -d raid10 /dev/sdb /dev/sdc /dev/sdd /dev/sd=
e
>
> and @,
>
>  "Churning Butter(FS): An Interview with Chris Mason"
>   http://www.linux-mag.com/id/7329
>
>     CM Today you can do this:
>     mkfs.btrfs -m raid1 -d raid10 /dev/sda /dev/sdb /dev/sdc /dev/sdd
> And you=92ll get metadata on raid1 and data on raid10. The raid10 wil=
l
> use all four drives and the raid1 will use two drives at a time. Yes,
> btrfs allows you to pick different values for data or metadata.
>
> The fact that I *can* setup data & metadata differently is clear.  Bu=
t
> I'm not at all clear *why* I'd want to, or what the advantages are.
> I'd guess it's a balance/combination of performance & resiliency.
>
> Naively "-m raid10 -d raid10" seems to make the most sense -- if i
> have it, use it.
>
> Are there any benchmarks, guidelines or recommendations?
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs=
" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>  =20

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Re: when/why to use diffferent raid values for btrfs data & metadata?

[0bo0]

hi

On Sun, Jan 24, 2010 at 3:28 AM, RK <rkasl@computer.org> wrote:
> try this article "Linux Don't Need No Stinkin' ZFS: BTRFS Intro &
> Benchmarks"
> http://www.linux-mag.com/id/7308/3/
> , there is a benchmark table and speed analysis (very informative), but
> all the benchmarks are done with same -m and -d mkfs.btrfs option

that's one of the articles i' read.  it also does mention that you can
define data/metadata as differnt RAID, afaict, it doesn't (?) say
anything about the what/why you would ... which is what i'm unclear
about.

thanks!

Re: when/why to use diffferent raid values for btrfs data & metadata?

[0bo0]

anyone on when/why to use different RAID geometries for data & metadata=
?

On Sun, Jan 24, 2010 at 8:38 AM, 0bo0 <0.bugs.only.0@gmail.com> wrote:
> hi
>
> On Sun, Jan 24, 2010 at 3:28 AM, RK <rkasl@computer.org> wrote:
>> try this article "Linux Don't Need No Stinkin' ZFS: BTRFS Intro &
>> Benchmarks"
>> http://www.linux-mag.com/id/7308/3/
>> , there is a benchmark table and speed analysis (very informative), =
but
>> all the benchmarks are done with same -m and -d mkfs.btrfs option
>
> that's one of the articles i' read. =A0it also does mention that you =
can
> define data/metadata as differnt RAID, afaict, it doesn't (?) say
> anything about the what/why you would ... which is what i'm unclear
> about.
>
> thanks!
>
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Re: when/why to use diffferent raid values for btrfs data & metadata?

[Goffredo Baroncelli]

On Saturday 06 February 2010, 0bo0 wrote:
> anyone on when/why to use different RAID geometries for data & metadata?
> 

I expected that the size of data and meta-data are different by several order 
of magnitude. So I can choice different trade-off between 
space/speed/reliability for data and/or metadata.

If I need speed I can put the meta-data in a "fast" raid (like raid10) and put 
the data in a slow raid (like raid6). 
Or if I can tolerate the lost of data, I can put the meta-data in raid1 and 
the data in raid0. A fault of a disk, may lead to lost of data, but not to 
lost of the meta-data (the file-system is fully working).


> On Sun, Jan 24, 2010 at 8:38 AM, 0bo0 <0.bugs.only.0@gmail.com> wrote:
> > hi
> >
> > On Sun, Jan 24, 2010 at 3:28 AM, RK <rkasl@computer.org> wrote:
> >> try this article "Linux Don't Need No Stinkin' ZFS: BTRFS Intro &
> >> Benchmarks"
> >> http://www.linux-mag.com/id/7308/3/
> >> , there is a benchmark table and speed analysis (very informative), but
> >> all the benchmarks are done with same -m and -d mkfs.btrfs option
> >
> > that's one of the articles i' read.  it also does mention that you can
> > define data/metadata as differnt RAID, afaict, it doesn't (?) say
> > anything about the what/why you would ... which is what i'm unclear
> > about.
> >
> > thanks!
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 


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Re: when/why to use diffferent raid values for btrfs data & metadata?

[0bo0]

On Sat, Feb 6, 2010 at 5:16 AM, Goffredo Baroncelli <kreijack@libero.it> wrote:
>> anyone on when/why to use different RAID geometries for data & metadata?
>>
>
> I expected that the size of data and meta-data are different by several order
> of magnitude. So I can choice different trade-off between
> space/speed/reliability for data and/or metadata.
>
> If I need speed I can put the meta-data in a "fast" raid (like raid10) and put
> the data in a slow raid (like raid6).
> Or if I can tolerate the lost of data, I can put the meta-data in raid1 and
> the data in raid0. A fault of a disk, may lead to lost of data, but not to
> lost of the meta-data (the file-system is fully working).

sounds like there's no further, subtle considerations beyond the usual
 "which RAID" considerations.  then, i suppose that as long as i find
RAID-10 "good enough"(as it has been in the md-case), there's no
compelling reason NOT tp place both data/metadata in RAID-10
constructs in btrfs.

thanks.