Hi,
On Fri, Mar 21, 2025 at 03:32:39PM -0400, Eben King wrote:
> I need to do something that ends up with a larger array using 3, maybe
> 4 disks. It'd be nice if it supports disks of disparate sizes (and
> actually uses the extra space), so I can upgrade by attrition.
It depends on how wedded you are to the idea of making use of more of
the caoacity of mismatched (capacity) devices.
md and zfs are both fine choices on Linux but in the case of mirrors
will only give you mirrors of the smallest device up until you have
both sides of the mirror with the larger device, then you can grow it
in place to the full capacity.
So for example, with your existing 2x1TB if you add 2x8TB or something,
you could:
1. Break your 1TB mirror
2. Add an 8TB drive as the other half of your mirror
3. Resync your mirror
4. Use removed 1TB drive and remaining 8TB drive to make another (1TB) mirror
5. LVM the two mirrors together to get 2TB usable space
6. At later date replace 1TB drives with more 8TB ones and grow it all
in place to two mirrors of 8TB usable each.
Or start again with ZFS and make the equivalent stripe of two mirror
vdevs that again is only two sets of 1TB until the small drives are
replaced and it can be grown in place.
Now, if you immediately want to obtain more capacity you could do it by
making separate arrays, i.e. keep the 1TB mirror and make an 8TB mirror
for a total 9TB usable. Obviously it's a pain having to manually decide
where to put data.
If you absolutely want the capacity and you absolutely must have it in
one array, you could do btrfs. It is great for making redundant use of
mixed size drives. With a "raid1" profile and the drive sizes described
you would get 9TB usable. The performance won't be predictable though
because you won't be able to control where the extents for the files go.
You would also be able to replace the smaller drives later on to get
higher usable capacity.
Here is a capacity calculator:
https://carfax.org.uk/btrfs-usage/?c=2&slo=1&shi=1&p=0&dg=1&d=8000&d=8000&d=1000&d=1000
>
On Fri, Mar 21, 2025 at 05:11:19PM -0400, Boyan Penkov wrote:
> If someone who has a firm grasp of the current state of btrfs vs bcachefs
> for "power users who still need to get stuff other than 'administrativia'
> done" would speak up, I'd be glad for some perspective as well...
bcachefs is not ready for production use and its upstream author
specifically has asked Debian users not to use it as they want only
people who use the latest userland tools to test it out and report
bugs.
https://lore.kernel.org/all/36xhap5tafvm4boiy3acu5kxlhkvnp32wp3oknbfbkxbdkeq7r@galecvidi3bn/
https://jonathancarter.org/2024/08/29/orphaning-bcachefs-tools-in-debian/
Thanks,
Andy
--
https://bitfolk.com/ -- No-nonsense VPS hosting
