possible to automount a software btrfs raid 5 at start?

[jzilla50]

Mint MATE 17Q on an SSD.
I made a btrfs raid 5 with 3 TB HDDs and everything was fine but then I realized that I always have to start the raid in the "control"/disk menu.

I tried to set it up manually in the /etc/fstab but it seems I have not enough experience because I endet up with a system in read only mode. And I don't understand some points in the DISK menu when I try to put it on autoconfiguration I will have a ro system as well. (I guess the menu and I will not be friends

I have no idea besides I have made some progress but there are blind spots because I use Mint for only 6 months now.

If there is a way let me now.

I know the btrfs sw raid is stupid but I'm testing it as iSCSI and Storage Cube.

[WharfRat]

jzilla50,

Can you

Code: Select all

ls -l /dev/mapper

with the raid active

[Mute Ant]

I have been running a BTRFS pair of old 80GB drives as my Rebecca [booting] system for two weeks now. You just mount 1 of the component partitions where you want it, the kernel seems to take care of finding and attaching the other components [no mapper as far as I can tell]. From the entry in /etc/fstab you can't tell it's RAID data, multiple device or anything special...

• /dev/sda1 / btrfs compress,autodefrag,noatime 0 0

...but I see 160GB system space.

Rebeca kernel version is 3.13.0-37-generic
Rebecca btrfs version is 3.12
Rebecca grub-pc version is 2.02~beta2-9ubuntu1

[jzilla50]

Hi WharfRat,

yes I did and I got this.

insgesamt 0
crw------- 1 root root 10, 236 Nov 27 22:09 control

:/ But it is working???

jzilla50,

Can you

Code: Select all

ls -l /dev/mapper

with the raid active

[jzilla50]

Hi Mute Ant,

aha I may not use /dev/md127 is that right? I always tried to use the name choosen by the system.

When I choose the first disk physical drive of the raid it should work do you think?

Don't want to kill this btrfs raid yet

I have been running a BTRFS pair of old 80GB drives as my Rebecca [booting] system for two weeks now. You just mount 1 of the component partitions where you want it, the kernel seems to take care of finding and attaching the other components [no mapper as far as I can tell]. From the entry in /etc/fstab you can't tell it's RAID data, multiple device or anything special...

• /dev/sda1 / btrfs compress,autodefrag,noatime 0 0

...but I see 160GB system space.

Rebeca kernel version is 3.13.0-37-generic
Rebecca btrfs version is 3.12
Rebecca grub-pc version is 2.02~beta2-9ubuntu1

[Mute Ant]

If you have /dev/md127 I have no idea how it will behave, sorry.

[mintybits]

A raid usually needs an ARRAY statement in /etc/madam/madam.conf

It also needs a mount point defined in /etc/fstab. The mount point has to exist. For example something like this

Code: Select all

/dev/md127    /media/raid  btrfs  defaults   0 2

You can call the array what you like in the ARRAY statement, eg: /dev/md1 so long as it is matched in fstab.

I think you can make an array statement using: sudo mdadm -Es

Please post the output of

Code: Select all

cat /proc/mdstat

[jzilla50]

Hi and thank you for your kind answers. This really helps to close some blind spots

mdadm.conf:
ARRAY /dev/md127 UUID=8d20etc

sudo mdadm -Es gives me:
ARRAY /dev/md/MyRAID5 metadata=1.2 UUID=8d20etc name=mypc:MyRAID5

cat /proc/mdstat
Personalitiers : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10]

md127 : active raid5 sdd[3] sdc[1] sdb[0]
5860270080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
bitmap: 0/22 pages [0KB], 65536KB chunk

unused devices: <none>


Mhrm...

ARRAY /dev/md/MyRAID5 and /dev/md127? Is this a bug or a feature?

A raid usually needs an ARRAY statement in /etc/madam/madam.conf

It also needs a mount point defined in /etc/fstab. The mount point has to exist. For example something like this

Code: Select all

/dev/md127    /media/raid  btrfs  defaults   0 2

You can call the array what you like in the ARRAY statement, eg: /dev/md1 so long as it is matched in fstab.

I think you can make an array statement using: sudo mdadm -Es

Please post the output of

Code: Select all

cat /proc/mdstat

[jzilla50]

Hej no problem I'm still learning and it is fun.

If you have /dev/md127 I have no idea how it will behave, sorry.

[mintybits]

Mhrm...

ARRAY /dev/md/MyRAID5 and /dev/md127? Is this a bug or a feature?

One person's bug is another person's feature.

The array device name in mdadm.conf needs to match the one in fstab.

[WharfRat]

jzilla50,

Maybe btrfs raid is handled differently, but when running a lvm or linux software raid the mapper shows the abstract devices. This is an lvm setup

Code: Select all

bill@4700 ~ $ ls -l /dev/mapper/
total 0
crw------- 1 root root 10, 236 2014-11-29 09:34:35 control
lrwxrwxrwx 1 root root       7 2014-11-29 09:34:38 vg0-home -> ../dm-1
lrwxrwxrwx 1 root root       7 2014-11-29 09:34:38 vg0-root -> ../dm-0
lrwxrwxrwx 1 root root       7 2014-11-29 09:34:38 vg0-shared -> ../dm-3
lrwxrwxrwx 1 root root       7 2014-11-29 09:34:38 vg0-swap -> ../dm-2

so the fstab entries will match the links

Code: Select all

/dev/mapper/vg0-root /               ext3    noatime,errors=remount-ro 0       1
/dev/mapper/vg0-home /home           ext3    defaults,noatime,errors=remount-ro        0       2
/dev/mapper/vg0-swap none            swap    sw              0       0
/dev/mapper/vg0-shared	/media/shared	ext3	defaults,errors=remount-ro,noatime	0	2

Since yours didn't show anything, I'll have to assume that btrfs raid differs from the usual mapping mechanisms