Hello!
I tried looking at the documentation for installing Fedora[1], but didn't see an explanation of what raid level "single" means in Anaconda. If I select two disks for a volume, and then select single level RAID, does this mean I'm actually only using one disk, or is it somehow equivalent to one of the other RAID levels, or something else entirely?
[1] https://docs.fedoraproject.org/en-US/fedora/f33/install-guide/install/Instal...
On 11/6/20 1:38 PM, Matti Pulkkinen wrote:
I tried looking at the documentation for installing Fedora[1], but didn't see an explanation of what raid level "single" means in Anaconda. If I select two disks for a volume, and then select single level RAID, does this mean I'm actually only using one disk, or is it somehow equivalent to one of the other RAID levels, or something else entirely?
In the custom partitioning, if you try to create a btrfs file system and have multiple disk selected, it gives you some raid options. I believe "single" creates one filesystem across both drives. The current recommendation is to not use any RAID options with btrfs right now. Use mdraid underneath instead.
[1] https://docs.fedoraproject.org/en-US/fedora/f33/install-guide/install/Instal...
The docs seem a little broken. The internal links don't work and I think some point to sections that don't exist.
Samuel Sieb kirjoitti 7.11.2020 klo 0.11:
In the custom partitioning, if you try to create a btrfs file system and have multiple disk selected, it gives you some raid options. I believe "single" creates one filesystem across both drives.
I was able to find an explanation that "single" more or less means data is written to whichever device has the most free space left, and only to that device.
The current recommendation is to not use any RAID options with btrfs right now. Use mdraid underneath instead.
Could you elaborate on why this is? Is there a way to select which type of RAID to use in Anaconda?
The docs seem a little broken. The internal links don't work and I think some point to sections that don't exist.
I noticed that too, but I thought it was just something wrong with my browser.
On 11/10/20 7:47 AM, Matti Pulkkinen wrote:
Samuel Sieb kirjoitti 7.11.2020 klo 0.11:
The current recommendation is to not use any RAID options with btrfs right now. Use mdraid underneath instead.
Could you elaborate on why this is? Is there a way to select which type of RAID to use in Anaconda?
There was an explanation a while back on the -devel list during the discussion about making btrfs the default. I think that RAID5 and 6 are not working well for some reason. RAID1 is ok, but just be aware that by default, you can't boot from a degraded RAID without fixing it first. https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/...
You can select the type from the drop-down where you saw "single".
On Tue, Nov 10, 2020, 1:04 PM Samuel Sieb samuel@sieb.net wrote:
On 11/10/20 7:47 AM, Matti Pulkkinen wrote:
Samuel Sieb kirjoitti 7.11.2020 klo 0.11:
The current recommendation is to not use any RAID options with btrfs right now. Use mdraid underneath instead.
Could you elaborate on why this is? Is there a way to select which type of RAID to use in Anaconda?
There was an explanation a while back on the -devel list during the discussion about making btrfs the default. I think that RAID5 and 6 are not working well for some reason. RAID1 is ok, but just be aware that by default, you can't boot from a degraded RAID without fixing it first.
You should get dropped to a shell where you can
mount -o degraded,subvol=root /sysroot exit
And then use 'btrfs replace' to replace old for new drive. Currently it requires new to be same size or bigger than old. Once it completes use 'btrfs filesystem resize'.
Write up on using Btrfs parity raid: https://lore.kernel.org/linux-btrfs/20200627032414.GX10769@hungrycats.org/
Most problems can be avoided by using raid1 for metadata (the filesystem itself), i.e.
mkfs.btrfs -mraid1 -draid5 Or mkfs.btrfs -mraid1c3 -draid6
But yeah, raid is not a backup
--- Chris Murphy
Samuel Sieb kirjoitti 10.11.2020 klo 22.04:
There was an explanation a while back on the -devel list during the discussion about making btrfs the default. I think that RAID5 and 6 are not working well for some reason. RAID1 is ok, but just be aware that by default, you can't boot from a degraded RAID without fixing it first. https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/...
Okay, I think that'll be fine because I'm mostly interested in RAID0 anyway.
On Wed, Nov 11, 2020 at 11:16 AM Matti Pulkkinen mkjpul@utu.fi wrote:
Samuel Sieb kirjoitti 10.11.2020 klo 22.04:
There was an explanation a while back on the -devel list during the discussion about making btrfs the default. I think that RAID5 and 6 are not working well for some reason. RAID1 is ok, but just be aware that by default, you can't boot from a degraded RAID without fixing it first. https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/...
Okay, I think that'll be fine because I'm mostly interested in RAID0 anyway.
That's stable on Btrfs so you can just choose that in the Volume->Modify menu, and choose raid0 there (instead of single). This only applies to data. It will still be raid1 metadata. That might seem odd. Don't think of a full drive failure but rather silent corruption on one of the drives - the file system itself will be able to detect that and self-heal without face planting. If a drive fully fails, then you're in this curious situation where you definitely won't be able to boot since half the OS is missing. But you could do a partial recovery of the files on the surviving drive. Most likely this is a big mess but some folks might find it useful.
Another way to do this is just select the two drives, and do an automatic installation. And then convert to raid0 after installation and reboot.
btrfs balance start -dconvert=raid0 /
On Tue, Nov 10, 2020, 8:47 AM Matti Pulkkinen mkjpul@utu.fi wrote:
Samuel Sieb kirjoitti 7.11.2020 klo 0.11:
In the custom partitioning, if you try to create a btrfs file system and have multiple disk selected, it gives you some raid options. I believe "single" creates one filesystem across both drives.
I was able to find an explanation that "single" more or less means data is written to whichever device has the most free space left, and only to that device.
Yeah, it allocates block groups to the device with most free space. It is possible to convert between profiles. And each block group type can have its own profile. Single is the mkfs and Anaconda default.
The current recommendation is to not use any RAID options with btrfs
right now. Use
mdraid underneath instead.
Could you elaborate on why this is? Is there a way to select which type of RAID to use in Anaconda?
Device type menu shows: btrfs, lvm, raid and standard. And raid means mdadm raid Custom partitioning keeps these devices types separate. But Advanced-Custom lets you do most anything,
It's a set of tradeoffs. In my case, I don't need unattended/automatic degraded boot. But i do want full integrity checking and self healing.
The docs seem a little broken. The internal links don't work and I
think some point to sections that don't exist.
I noticed that too, but I thought it was just something wrong with my browser.
Is it broken for 32 and 31? Our just 33?
-- Chris Murphy
On 11/10/20 11:14 PM, Chris Murphy wrote:
On Tue, Nov 10, 2020, 8:47 AM Matti Pulkkinen <mkjpul@utu.fi mailto:mkjpul@utu.fi> wrote: > The current recommendation is to not use any RAID options with btrfs right now. Use > mdraid underneath instead.
Could you elaborate on why this is? Is there a way to select which type of RAID to use in Anaconda?
Device type menu shows: btrfs, lvm, raid and standard. And raid means mdadm raid Custom partitioning keeps these devices types separate. But Advanced-Custom lets you do most anything,
I assumed he was asking how to pick the btrfs raid types, but I might be wrong.
> The docs seem a little broken. The internal links don't work and I > think some point to sections that don't exist. I noticed that too, but I thought it was just something wrong with my browser.
Is it broken for 32 and 31? Our just 33?
I just checked and the docs for 31 and 32 have the same problem.
Chris Murphy kirjoitti 11.11.2020 klo 9.14:
Device type menu shows: btrfs, lvm, raid and standard. And raid means mdadm raid Custom partitioning keeps these devices types separate. But Advanced-Custom lets you do most anything,
Ah, of course. I don't know why I didn't think to look there. Thanks again!