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partition question

DISCUSSION Roelof Wobben 6 participants 7 messages Jan 11, 2013 – Jan 16, 2013 Btrfs file system

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#0 lore raw

Hello,

I have one thing I think I don't really understand about btrfs,

Normally if I use ext4 I make a 3 partitions for my distro.

one for boot about 1G
one for home about 30G
one for root for the rest of my 100G.

Now I wonder if I want to do the same with btrfs.

Can I do the same so make 3 partitions with btrfs or can I better make 1 partiton of 100G and make the /boot /home and / subvolumes of the big partitiion.

Can one of you btfrs gurus shine a light of this matter ?

Regards,

Roelof Wobben

#1 lore raw
Quoted 10 lines · Roelof Wobben

Hello,

I have one thing I think I don't really understand about btrfs,

Normally if I use ext4 I make a 3 partitions for my distro.

one for boot about 1G
one for home about 30G
one for root for the rest of my 100G.

Quoted 5 lines

Now I wonder if I want to do the same with btrfs.

Can I do the same so make 3 partitions with btrfs or can I better make 1 partiton of 100G and make the /boot /home and / subvolumes of the big partitiion.

Well. what is your motivation for doing it that way in the ext4?

If you're looking to be able to selectively mount sections of your filesystem, then sure, subvolumes might work, but a lot of people divide partitions this way so that they'd be independent for purposes of reliability. Subvolumes of one btrfs partition wouldn't provide that independence.

~Chris

#2 lore raw
In reply to Roelof Wobben
Quoted 10 lines · Roelof Wobben

Hello,

I have one thing I think I don't really understand about btrfs,

Normally if I use ext4 I make a 3 partitions for my distro.

one for boot about 1G
one for home about 30G
one for root for the rest of my 100G.

Quoted 5 lines

Now I wonder if I want to do the same with btrfs.

Can I do the same so make 3 partitions with btrfs or can I better make 1 partiton of 100G and make the /boot /home and / subvolumes of the big partitiion.

Can one of you btfrs gurus shine a light of this matter ?

You can make one Btrfs volume with /boot, /home, and / as subvolumes. GRUB2 2.00 can boot this arrangement, and that's the first caveat which is that many distributions are using older versions of GRUB2. It even works with Btrfs data/metadata profiles single, dup; and multiple device raid 0, 1, 10; and compression zlib, and lzo.

Swap still needs to be on a separate partition, as I don't think Btrfs is supporting swapfiles yet still, but maybe someone else can comment on the status of that.

While GRUB2 has LUKS support, its easier to have /boot on a separate partition for such purposes.

The limiting factor is an installer that doesn't offer the unified option, and also won't install to a pre-configured Btrfs volume. I can vouch for Fedora 18, which can do both. That is, it will install to an existing Btrfs volume either reusing or creating subvols for home, boot, usr, var; and it will compel you to create a new subvol for root. Further, it can create new Btrfs volumes. By default with the non-custom partition path, it will put /boot on ext4. If you choose BTRFS in Installation Options > Partition scheme configuration *before* you get to custom partitioning (the screen labeled Manual Partitioning), you will be able to add a Boot mountpoint and change it from ext4 to Btrfs, and set the size however large you want. Any additional mount points other than swap will be created as subvolumes.

Chris Murphy

#3 lore raw
Quoted 22 lines · Chris Murphy
Quoted 8 lines · Roelof Wobben

I have one thing I think I don't really understand about btrfs,

Normally if I use ext4 I make a 3 partitions for my distro.

one for boot about 1G
one for home about 30G
one for root for the rest of my 100G.

Quoted 5 lines

Now I wonder if I want to do the same with btrfs.

Can I do the same so make 3 partitions with btrfs or can I better make 1 partiton of 100G and make the /boot /home and / subvolumes of the big partitiion.

Can one of you btfrs gurus shine a light of this matter ?

You can make one Btrfs volume with /boot, /home, and / as subvolumes. GRUB2 2.00 can boot this arrangement, and that's the first caveat which is that many distributions are using older versions of GRUB2. It even works with Btrfs data/metadata profiles single, dup; and multiple device raid 0, 1, 10; and compression zlib, and lzo.

Quoted 3 lines

Swap still needs to be on a separate partition, as I don't think Btrfs is supporting swapfiles yet still, but maybe someone else can comment on the status of that.

I don't know this area of the code at all well, but as I understand
it, there's been some work in the kernel (swap over NFS) which lays down some of the underlying infrastructure we'd need to support swapfiles on btrfs, but we don't have anything beyond that. I don't know of anyone working on it, either.

Hugo.

Signature · 3 lines
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
       --- It's against my programming to impersonate a deity! ---       
#4 lore raw

Op 11-1-2013 23:38, Hugo Mills schreef:

Quoted 25 lines · Chris Murphy
Quoted 21 lines · Roelof Wobben
Quoted 8 lines

I have one thing I think I don't really understand about btrfs,

Normally if I use ext4 I make a 3 partitions for my distro.

one for boot about 1G
one for home about 30G
one for root for the rest of my 100G.

Quoted 5 lines

Now I wonder if I want to do the same with btrfs.

Can I do the same so make 3 partitions with btrfs or can I better make 1 partiton of 100G and make the /boot /home and / subvolumes of the big partitiion.

Can one of you btfrs gurus shine a light of this matter ?

You can make one Btrfs volume with /boot, /home, and / as subvolumes. GRUB2 2.00 can boot this arrangement, and that's the first caveat which is that many distributions are using older versions of GRUB2. It even works with Btrfs data/metadata profiles single, dup; and multiple device raid 0, 1, 10; and compression zlib, and lzo.

Quoted 3 lines

Swap still needs to be on a separate partition, as I don't think Btrfs is supporting swapfiles yet still, but maybe someone else can comment on the status of that.

Quoted 8 lines

I don't know this area of the code at all well, but as I understand
it, there's been some work in the kernel (swap over NFS) which lays down some of the underlying infrastructure we'd need to support swapfiles on btrfs, but we don't have anything beyond that. I don't know of anyone working on it, either.

Hugo.

Im testing Crux where I must make a custom partiion scheme before I can start the installer. And Im making this scheme before because people told me that was the best way to work.

Roelof

#5 lore raw
In reply to Hugo Mills
Quoted 8 lines

I don't know this area of the code at all well, but as I understand
it, there's been some work in the kernel (swap over NFS) which lays down some of the underlying infrastructure we'd need to support swapfiles on btrfs, but we don't have anything beyond that. I don't know of anyone working on it, either.

Hugo.

You can use swapfile on btrfs with mounting it via a loop device. It won't be incredibly fast, but it will work.

#6 lore raw
In reply to Hugo Mills
Quoted 10 lines · Hugo Mills
Quoted 3 lines · Chris Murphy

Swap still needs to be on a separate partition, as I don't think Btrfs is supporting swapfiles yet still, but maybe someone else can comment on the status of that.

I don't know this area of the code at all well, but as I understand
it, there's been some work in the kernel (swap over NFS) which lays down some of the underlying infrastructure we'd need to support swapfiles on btrfs, but we don't have anything beyond that. I don't know of anyone working on it, either.

Nobody up to my knowledge.

david