On 28/10/2021 14:36, David T-G wrote:
Hi, all --
It's time to replace a few 4T disks in our little server. I don't
particularly want to go back with more 4T disks (although the same
model sure are cheap these days! :-) and figure I should put in larger
drives as I go. I am then left with weighing simple $/G vs total price;
bigger drives can be cheaper per volume but of course more overall.
My first approach is to put newer, larger drives in place and expect to
grow into the empty space when all of the old ones have been swapped out.
But ... If I were to splurge and buy 3ea big drives to replace all of
Does that mean you have three drives currently?
the space that I have now, how practical is it to grow that RAID5 array
by adding additional drives later?
Very. mdadm --add ...
My eventual goal would be to get
to 8-10 devices in a RAID6 layout (two "extras"), but of course I can't
afford that today. Do I have an easy path to get there in the long run?
[BTW, can I convert an array from RAID5 to RAID6, too?]
On the other hand, I do have the empty slots (currently filled with
scratch drives here and there), so I could both replace my aging drives
and add more and just grow this array 1) if the growth idea is practical
and 2) if I don't get to splurge.
Okay, buy your new 8TB drives in pairs (unless you've got a bunch of
scratch 4TB drives).
Assuming you've got a 3x4TB array this will get you to a 3x8TB in one hit...
mdadm --replace 4TB with 8TB
Twice.
mdadm --create --level=striped 4TB 4TB (to give you an 8TB raid0)
mdadm --replace 4TB with 8TB raid0 mirror
You may then be able move the data off your scratch drives onto the
array, create another 8TB raid0, and add that for a raid6. You can then
just add 8TB drives bit by bit.
Read the website - there#s a lot of info there...
https://raid.wiki.kernel.org/index.php/Linux_Raid
Cheers,
Wol
