Who way mirror in BRTFS

Who way mirror in BRTFS

[Jaromir Zdrazil]

Hi Jan,

   sorry to borther you, but I need some info and you are propably the best one to answer.

   I am planing now a new backup system (servers) for a medical company. My idea is to have a dedicated backup server in each building and wia two way mirror mirror it to another server in diff building (bacause of security) through fs. ZFS is capable, but i would like to stick to a Linux.
   As I understand, there is some work done in two way mirror in brtfs (which seems to me as best solustion for that under linux) and you are the one working on that.

   My Qs are:
- do you know any better fs for this purpose, other than brtfs under Linux?
- What is the implementation of two way mirror in brtfs, and when do you expect to have it done to a degree so I can try it? Tt does not have to work now, but it should work next year ;O)

I have 20years experience in linux, and if I do not have to debug anything, I am more less happy ;O)

Thank you very much! Jaromir

Two way mirror in BRTFS

[Jaromir Zdrazil]

Sorry fo the typo in the subject!

Just to add, I would like to see a two way mirror solution, but if it w=
ill not work now/is not implemnted yet, I would propably choose between=
 drbd in asynchronous mode or make a some kind if "incremental" snapsho=
t to a remote mapped disk (I do not know yet, if brtfs support it)  - i=
t means have one shapshop and let's say have a daily incremental update=
 of this snapshot.

How would you do it?

I have never used btrfs, baucause in "brtfs home page" is still written=
 experimental, and lately with three kids I have less and less time to =
experiment ... but, as I found some short time ago, there is laso a sug=
gestion to use it ... and I know it is used more and more frequently ..=
=2E so i will give it a try.

Btw when is a plan to move it from experimental? ;o)

Have to look at the source code a bit (hope there are some notes about =
future). Jaromir

> ------------ P=F9vodn=ED zpr=E1va ------------
> Od: Jaromir Zdrazil <jaromir.zdrazil@email.cz>
> P=F8edm=ECt: Who way mirror in BRTFS
> Datum: 30.12.2011 12:55:44
> ----------------------------------------
> Hi Jan,
>=20
>    sorry to borther you, but I need some info and you are propably th=
e best one
> to answer.
>=20
>    I am planing now a new backup system (servers) for a medical compa=
ny. My idea
> is to have a dedicated backup server in each building and wia two way=
 mirror
> mirror it to another server in diff building (bacause of security) th=
rough fs.
> ZFS is capable, but i would like to stick to a Linux.
>    As I understand, there is some work done in two way mirror in brtf=
s (which
> seems to me as best solustion for that under linux) and you are the o=
ne working
> on that.
>=20
>    My Qs are:
> - do you know any better fs for this purpose, other than brtfs under =
Linux?
> - What is the implementation of two way mirror in brtfs, and when do =
you expect
> to have it done to a degree so I can try it? Tt does not have to work=
 now, but
> it should work next year ;O)
>=20
> I have 20years experience in linux, and if I do not have to debug any=
thing, I am
> more less happy ;O)
>=20
> Thank you very much! Jaromir
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs=
" in
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Re: Two way mirror in BRTFS

[Fajar A. Nugraha]

2011/12/30 Jaromir Zdrazil <jaromir.zdrazil@email.cz>:
> Sorry fo the typo in the subject!
>
> Just to add, I would like to see a two way mirror solution, but if it=
 will not work now/is not implemnted yet, I would propably choose betwe=
en drbd in asynchronous mode or make a some kind if "incremental" snaps=
hot to a remote mapped disk (I do not know yet, if brtfs support it) =A0=
- it means have one shapshop and let's say have a daily incremental upd=
ate of this snapshot.

You mean like "zfs send -i"? If yes, why not just use zfs? There's
zfsonlinux project, with easy-to-install ppa for ubuntu. Or you could
compile it manually.

>
> How would you do it?

If you DO mean zfs-send-like-functionality, then you should ask about
"btrfs send and receive", not "two way mirror" (which is not an
accurate way to describe what you want). Also, send/receive ability
does not mean it can act as two-way mirror. It CAN be an alternative
to drbd async though.

I don't think there's any publicly available code for it yet though.

--=20
=46ajar
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Re: Re: Two way mirror in BRTFS

[Jaromir Zdrazil]

> ------------ P=F9vodn=ED zpr=E1va ------------
> Od: Fajar A. Nugraha <list@fajar.net>
> P=F8edm=ECt: Re: Two way mirror in BRTFS
> Datum: 30.12.2011 14:27:39
> ----------------------------------------
> 2011/12/30 Jaromir Zdrazil <jaromir.zdrazil@email.cz>:
> > Sorry fo the typo in the subject!
> >
> > Just to add, I would like to see a two way mirror solution, but if =
it will not
> work now/is not implemnted yet, I would propably choose between drbd =
in
> asynchronous mode or make a some kind if "incremental" snapshot to a =
remote
> mapped disk (I do not know yet, if brtfs support it) =A0- it means ha=
ve one
> shapshop and let's say have a daily incremental update of this snapsh=
ot.
>=20
> You mean like "zfs send -i"? If yes, why not just use zfs? There's
> zfsonlinux project, with easy-to-install ppa for ubuntu. Or you could
> compile it manually.
>=20
Thank you for your suggestion. As I know, there is not everything porte=
d yet, and one of the missing important features I plan to use is to cr=
ypt fs. And if I am not mistaken, current version does not yet support =
a mountable filesystem.
> >
> > How would you do it?
>=20
> If you DO mean zfs-send-like-functionality, then you should ask about
> "btrfs send and receive", not "two way mirror" (which is not an
> accurate way to describe what you want). Also, send/receive ability
> does not mean it can act as two-way mirror. It CAN be an alternative
> to drbd async though.

If I understand it correctly, the diff between send and receive and two=
 way mirror is that one is synchronous and the other is not (sends the =
signal that the file have been succesfully written after all/one instan=
ce have been succesfully written).
Maybe you can explain it a bit more.
>=20
> I don't think there's any publicly available code for it yet though.
>=20
Thank you. Jaromir
> --=20
> Fajar
> --
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Re: Re: Two way mirror in BRTFS

[Fajar A. Nugraha]

2011/12/30 Jaromir Zdrazil <jaromir.zdrazil@email.cz>:
>> > Just to add, I would like to see a two way mirror solution, but if=
 it will not
>> work now/is not implemnted yet, I would propably choose between drbd=
 in
>> asynchronous mode or make a some kind if "incremental" snapshot to a=
 remote
>> mapped disk (I do not know yet, if brtfs support it) =A0- it means h=
ave one
>> shapshop and let's say have a daily incremental update of this snaps=
hot.
>>
>> You mean like "zfs send -i"? If yes, why not just use zfs? There's
>> zfsonlinux project, with easy-to-install ppa for ubuntu. Or you coul=
d
>> compile it manually.
>>
> Thank you for your suggestion. As I know, there is not everything por=
ted yet, and one of the missing important features I plan to use is to =
crypt fs.

correct. But btrfs doesn't do encryption as well.
And if you're thinking of using luks/dm-crupt to provide encryption
for btrfs, there's nothing preventing you to use the same thing with
zfs.

> And if I am not mistaken, current version does not yet support a moun=
table filesystem.

You're mistaken :) With some extra work, you can even use it as root:
- http://zfsonlinux.org/example-zpl.html
- https://github.com/dajhorn/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Nat=
ive-ZFS-Root-Filesystem

>> >
>> > How would you do it?
>>
>> If you DO mean zfs-send-like-functionality, then you should ask abou=
t
>> "btrfs send and receive", not "two way mirror" (which is not an
>> accurate way to describe what you want). Also, send/receive ability
>> does not mean it can act as two-way mirror. It CAN be an alternative
>> to drbd async though.
>
> If I understand it correctly, the diff between send and receive and t=
wo way mirror is that one is synchronous and the other is not (sends th=
e signal that the file have been succesfully written after all/one inst=
ance have been succesfully written).
> Maybe you can explain it a bit more.

Two way: A replicates changes to B, and B can replicate it's own change=
s to A
One way: A replicates changes to B, but B can not replicate it's own
changes to A

While drbd only supports synchronous mode for active-active setup, the
generic "two way replication" does not have to be so. Also, just
because something is synchronous does not automatically mean it
supports two-way replication.

Either way, neither zfs or the (planned) btrfs send/receive supports
two-way/active-active setup. Both should (or will) work just fine for
one-way replication.

--=20
=46ajar
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Re: Re: Re: Two way mirror in BRTFS

[Jaromir Zdrazil]

> ------------ P=F9vodn=ED zpr=E1va ------------
> Od: Fajar A. Nugraha <list@fajar.net>
> P=F8edm=ECt: Re: Re: Two way mirror in BRTFS
> Datum: 30.12.2011 15:34:02
> ----------------------------------------
> 2011/12/30 Jaromir Zdrazil <jaromir.zdrazil@email.cz>:
> >> > Just to add, I would like to see a two way mirror solution, but =
if it will
> not
> >> work now/is not implemnted yet, I would propably choose between dr=
bd in
> >> asynchronous mode or make a some kind if "incremental" snapshot to=
 a remote
> >> mapped disk (I do not know yet, if brtfs support it) =A0- it means=
 have one
> >> shapshop and let's say have a daily incremental update of this sna=
pshot.
> >>
> >> You mean like "zfs send -i"? If yes, why not just use zfs? There's
> >> zfsonlinux project, with easy-to-install ppa for ubuntu. Or you co=
uld
> >> compile it manually.
> >>
> > Thank you for your suggestion. As I know, there is not everything p=
orted yet,
> and one of the missing important features I plan to use is to crypt f=
s.
>=20
> correct. But btrfs doesn't do encryption as well.

I thought it does. Hmm, don't know why ;O)

> And if you're thinking of using luks/dm-crupt to provide encryption
> for btrfs, there's nothing preventing you to use the same thing with
> zfs.
>=20
> > And if I am not mistaken, current version does not yet support a mo=
untable
> filesystem.
>=20
> You're mistaken :) With some extra work, you can even use it as root:
> - http://zfsonlinux.org/example-zpl.html
> -
> https://github.com/dajhorn/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Nat=
ive-ZFS-Root-Filesystem
>=20
It seems I trust the web pages too much - in http://zfsonlinux.org/ is =
written that it does not ;O)) otherwise I would be using it already.

> >> >
> >> > How would you do it?
> >>
> >> If you DO mean zfs-send-like-functionality, then you should ask ab=
out
> >> "btrfs send and receive", not "two way mirror" (which is not an
> >> accurate way to describe what you want). Also, send/receive abilit=
y
> >> does not mean it can act as two-way mirror. It CAN be an alternati=
ve
> >> to drbd async though.
> >
> > If I understand it correctly, the diff between send and receive and=
 two way
> mirror is that one is synchronous and the other is not (sends the sig=
nal that
> the file have been succesfully written after all/one instance have be=
en
> succesfully written).
> > Maybe you can explain it a bit more.
>=20
> Two way: A replicates changes to B, and B can replicate it's own chan=
ges to A
> One way: A replicates changes to B, but B can not replicate it's own
> changes to A
>=20
Of course.

> While drbd only supports synchronous mode for active-active setup, th=
e
> generic "two way replication" does not have to be so. Also, just
> because something is synchronous does not automatically mean it
> supports two-way replication.
>=20
Correct.

> Either way, neither zfs or the (planned) btrfs send/receive supports
> two-way/active-active setup. Both should (or will) work just fine for
> one-way replication.
>=20
That is what I needed to know! Thank you very much!

Jaromir
> --=20
> Fajar
> --
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Re: Re: Re: Two way mirror in BRTFS

[Niels de Carpentier]

> It seems I trust the web pages too much - in http://zfsonlinux.org/ is
> written that it does not ;O)) otherwise I would be using it already.

>From the website:

Please keep in mind the current 0.5.2 stable release does not yet support
a mountable filesystem. This functionality is currently available only in
the 0.6.0-rc6 release candidate.

Seems clear to me :)

Niels

Re: Re: Re: Two way mirror in BRTFS

[Fajar A. Nugraha]

2011/12/30 Jaromir Zdrazil <jaromir.zdrazil@email.cz>:
>> > And if I am not mistaken, current version does not yet support a mountable
>> filesystem.
>>
>> You're mistaken :) With some extra work, you can even use it as root:
>> - http://zfsonlinux.org/example-zpl.html
>> -
>> https://github.com/dajhorn/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Native-ZFS-Root-Filesystem
>>
> It seems I trust the web pages too much - in http://zfsonlinux.org/ is written that it does not ;O)) otherwise I would be using it already.

The web page is correct.
http://zfsonlinux.org/: "Please keep in mind the current 0.5.2 stable
release does not yet support a mountable filesystem. This
functionality is currently available only in the 0.6.0-rc6 release
candidate."
http://zfsonlinux.org/example-zpl.html: "However, all the core
functionality is in place and most of the advanced features are
working. Stability of the latest release candidates has been very good
and performance is respectible. Many people are successfully using the
ZFS on Linux release candidates."

Most zfsonlinux users use 0.6.0-rc6, and a big part of those is using
the easy-to-install package from ubuntu ppa.

>> Either way, neither zfs or the (planned) btrfs send/receive supports
>> two-way/active-active setup. Both should (or will) work just fine for
>> one-way replication.
>>
> That is what I needed to know! Thank you very much!

You're welcome.

-- 
Fajar

Re: Re: Two way mirror in BRTFS

[Niels de Carpentier]

>>
>> You mean like "zfs send -i"? If yes, why not just use zfs? There's
>> zfsonlinux project, with easy-to-install ppa for ubuntu. Or you could
>> compile it manually.
>>
> Thank you for your suggestion. As I know, there is not everything ported
> yet, and one of the missing important features I plan to use is to crypt
> fs. And if I am not mistaken, current version does not yet support a
> mountable filesystem.

You are mistaken :) The current version is pretty stable, as long as you
don't use compression or dedup. Some problems have been reported with
weird setups (USB disks for example), but I haven't seen any reports of
unrecoverable filesystems.

For btrfs bugs are still fixed on a daily basis, and some reports of
people with corrupted and unrecoverable filesystems.

Neither supports encryption.

I might consider ZFS for a production environment (although it's
officially not production ready), but I don't think btrfs is ready for
that yet. If you want to be safe, use ext4 with drbd or rsync.

Niels

Re: Re: Two way mirror in BRTFS

[cwillu]

> For btrfs bugs are still fixed on a daily basis, and some reports of
> people with corrupted and unrecoverable filesystems.

I don't know that there's been any actual unrecoverable filesystems
recently; unmountable is by far the more common issue, and given that
most sane people aren't putting their only copy of important
information on btrfs filesystems, their preference tends to be towards
wiping and starting over rather than spending a week to recover the
information by hand (the recovery tools that exist are the results of
the few who chose the other option).

I think "... people with corrupted and not easily recoverable" would
be a better summary.

Re: Re: Two way mirror in BRTFS

[Niels de Carpentier]

>> For btrfs bugs are still fixed on a daily basis, and some reports of
>> people with corrupted and unrecoverable filesystems.
>
> I don't know that there's been any actual unrecoverable filesystems
> recently; unmountable is by far the more common issue, and given that
> most sane people aren't putting their only copy of important
> information on btrfs filesystems, their preference tends to be towards
> wiping and starting over rather than spending a week to recover the
> information by hand (the recovery tools that exist are the results of
> the few who chose the other option).
>
> I think "... people with corrupted and not easily recoverable" would
> be a better summary.

Yes, you are right, in most cases most/all of the data is recoverable.
There was this case:

http://article.gmane.org/gmane.comp.file-systems.btrfs/14755

But that one might be recoverable as well.

I'm sure btrfs will become the main linux filesystem of the future, it's
just not there yet. The mythical btrfsck might change this. But neither
btrfs or zfs on linux should currently be used for important production
systems.

Niels

Re: Re: Re: Two way mirror in BRTFS

[Jaromir Zdrazil]

> ------------ P=F9vodn=ED zpr=E1va ------------
> Od: Niels de Carpentier <niels@decarpentier.com>
> P=F8edm=ECt: Re: Re: Two way mirror in BRTFS
> Datum: 30.12.2011 16:15:51
> ----------------------------------------
> >>
> >> You mean like "zfs send -i"? If yes, why not just use zfs? There's
> >> zfsonlinux project, with easy-to-install ppa for ubuntu. Or you co=
uld
> >> compile it manually.
> >>
> > Thank you for your suggestion. As I know, there is not everything p=
orted
> > yet, and one of the missing important features I plan to use is to =
crypt
> > fs. And if I am not mistaken, current version does not yet support =
a
> > mountable filesystem.
>=20
> You are mistaken :) The current version is pretty stable, as long as =
you
> don't use compression or dedup. Some problems have been reported with
> weird setups (USB disks for example), but I haven't seen any reports =
of
> unrecoverable filesystems.
>=20
Thank you for the info. What I wanted from the fs was 108% acuracy, cry=
pt fs, at least some kind one way mirror, two way would be best and com=
pression of the fs would be nice.

Now it seems, that neither of the fsses cancrypt under linux, ZFS is ac=
curate&can reconstruct, BTRFS is accurate&can reconstruct only in mirro=
r, BTRFS can make live incremental backups/snapshots, ZFS can make also=
 send ... and one or two way mirror are future plans for linux ;O)

> For btrfs bugs are still fixed on a daily basis, and some reports of
> people with corrupted and unrecoverable filesystems.
>=20
> Neither supports encryption.
>=20
> I might consider ZFS for a production environment (although it's
> officially not production ready), but I don't think btrfs is ready fo=
r
> that yet. If you want to be safe, use ext4 with drbd or rsync.
>=20
> Niels
>=20
Hmm, I have concluded this afternoon, than ZFS under linux does not hav=
e what I would like to have, but there seems no better solution under l=
inux for now ... thanks for your experience! It helps me a lot. Jaromir
>=20
>=20
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