On Sun, Nov 27, 2022 at 07:21:16PM +0100, Reindl Harald wrote:

Am 27.11.22 um 15:10 schrieb piergiorgio.sartor@nexgo.de:

quoted

November 27, 2022 at 12:46 PM, "Reindl Harald" [off-list ref] wrote:

quoted

Am 26.11.22 um 21:02 schrieb John Stoffel:

quoted

I call it a failure of the layering model. If you want RAID, use MD.
  If you want logical volumes, then put LVM on top. Then put
  filesystems into logical volumes.
  So much simpler...

have you ever replaced a 6 TB drive and waited for the resync of mdadm in the hope in all that hours no other drive goes down?

when your array is 10% used it's braindead
when your array is new and empty it's braindead

ZFS/BTRFS don't neeed to mirror/restore 90% nulls

You cannot consider the amount of data in the
array as parameter for reliability

If the array is 99% full, MD or ZFS/BTRFS have
same behaviour, in terms of reliability.
If the array is 0% full, as well

you completly miss the point!

if your mdadm-array is built with 6 TB drivres wehn you replace a drive you
need to sync 6 TB no matter if 10 MB or 5 TB are actually used

I'm not missing the point, you're not
understanding the consequences of
your way of thinking.

If the ZFS/BTRFS is 99% full, how much
time will it need to be synched?

The same (more or less) of MD.

So, what's the difference in *this* case?

None.

This means the risk of (you wrote, I believe)
an other disk to go down is the same.

This means that you're considering the
reliability as function of how much
the array is full (or empty).

No matter if MD takes *always* full time.
It's not the point, in relation to reliability.

In other word, ZFS/BTRFS optimize the sync
time, for sure, but this should *not* be
considered when thinking in terms of
reliability.

bye,

-- 

piergiorgio