Re: Nothing wrong, but is my website advice wonky?

["John Stoffel" <john@stoffel.org>]

>>>>> "Wol" == Wol  <antlists@youngman.org.uk> writes:

Wol> On 28/11/2021 20:15, John Stoffel wrote:
>>>>>>> "Wol" == Wol  <antlists@youngman.org.uk> writes:
>> 
Wol> Problem solved! My usual problem of missing the detail...
>> 
>> How was the problem solved?  Can you provide details on the before and
>> after setup?  It should be trivial to test with loop back devices.
>> 
Wol> I'd described starting with a 2-drive mirror and converting it to
Wol> a 3-drive raid-5. I was actually starting with a 2-active-1-spare
Wol> mirror ...

Wol> So I converted it to raid-5, and because there were only two active 
Wol> drives, it carried on running as a degraded two-drive raid-5.

Wol> Once I brought the spare into service with --raid-devices=3, it started 
Wol> reshaping.

Ah... that explains it.  

Wol> The website said to add the new drive and set raid-devices to three, I 
Wol> misread my own stuff and thought simply converting to raid-5 would bring 
Wol> in the spare.

>> So if you had removed the spare before hand, would it have jumped
>> straight to a three drive RAID 5 setup? 

Wol> No - because I didn't tell it to use all three drives.

>> And curious why you didn't
>> goto RAID6?  RAID5 just makes me nervous these days, I don't trust it
>> since drives tend to fail in waves.

Wol> Well, with two DVD drives and a floppy in an old chassis, I've
Wol> only got room for three drives. Well, there should be room for
Wol> four, but my drives are a bit too fat ... :-)

I understand.  We all have to work within our limits.  

Wol> Plus (1) I've had no trouble so far with my drives (famous last words), 
Wol> (2) the drives are two new Ironwolves and an old Barracuda so I'm only 
Wol> likely to lose one so long as I keep an eye on things, and (3) all the 
Wol> drives have dm-integrity on them, so a corrupt drive should sort itself out.

>> But in my home system, I also mostly just mirror (or even triple
>> mirror!) my important data for both speed and ease of recovery.
>> 
Wol> The trouble with a plain mirror is if your data is corrupted ...

Wol> And if you've got raid you need to keep an eye on it. I'm planning to 
Wol> get an 8TB drive for backups ... probably configure it to snapshot once 
Wol> a week (I'm running lvm over raid over dm-integrity) and then use rsync 
Wol> to back up the volume over the network. Mind you I'm going to have to 
Wol> learn a lot of rsync - configure client/server and then get it to back 
Wol> up just the one file ...

I've got an external USB-3 4tb drive I'm running rclone to, and
planning on taking it to the bank one of these days when I remember to
do so.