moving a working array

moving a working array

[o1bigtenor]

Greetings

I have a working (no issues) raid-10 array in one box.

Want to move it to another (new) box.

Please - - - a list of the software steps?

(the physical moving is the easy part - - - the new box has room
for a lot of drives and is ready for these 4 easily)

Just don't want a fubar situation because I've taken the wrong order
or even wrong steps.

The section 'using the array' has information but I'm not sure how
that will work moving from one box to the other.

(One question would be if the uuid of the array will remain the same
as that would make things easier - - - I could copy the uuid from the
existing and then just do the # mdadm --scan --assemble --uuid= blahblah )

TIA

Re: moving a working array

[Wilson Jonathan]

On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
> Greetings
> 
> I have a working (no issues) raid-10 array in one box.
> 
> Want to move it to another (new) box.
> 
> Please - - - a list of the software steps?
> 
> (the physical moving is the easy part - - - the new box has room
> for a lot of drives and is ready for these 4 easily)
> 
> Just don't want a fubar situation because I've taken the wrong order
> or even wrong steps.

First make a backup...

Second check the backup...

Third make another backup...

Fourth check that backup as well...

Move disks... (I personally have just amended the /etc/mdadm/mdadm.conf
file to include the uuid prior to moving disks and been good to go. BUT
if I'd have lost all the data, without backups, I'd not have been
fussed as it could all have been recreated/downloaded so I guess it all
depends on how important or unique the data is.)

But if you've got a new machine, why not get new disks and set up a
nice new clean raid and then just rsync the data accross. That way your
old disks become the backup, to the data you've newly transfered to
clean a clean array. 

> 
> The section 'using the array' has information but I'm not sure how
> that will work moving from one box to the other.
> 
> (One question would be if the uuid of the array will remain the same
> as that would make things easier - - - I could copy the uuid from the
> existing and then just do the # mdadm --scan --assemble --uuid=
> blahblah )
> 
> TIA

Re: moving a working array

[Wols Lists]

On 24/06/2022 15:09, Wilson Jonathan wrote:
> On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
>> Greetings
>>
>> I have a working (no issues) raid-10 array in one box.

Bummer. It's a raid-10. A raid-1 would have been easier.
>>
>> Want to move it to another (new) box.
>>
>> Please - - - a list of the software steps?
>>
>> (the physical moving is the easy part - - - the new box has room
>> for a lot of drives and is ready for these 4 easily)
>>
>> Just don't want a fubar situation because I've taken the wrong order
>> or even wrong steps.
> 
> First make a backup...
> 
> Second check the backup...
> 
> Third make another backup...
> 
> Fourth check that backup as well...

Seconded. And thirded and fourthed.

Actually, that might not be necessary ...
> 
> Move disks... (I personally have just amended the /etc/mdadm/mdadm.conf
> file to include the uuid prior to moving disks and been good to go. BUT
> if I'd have lost all the data, without backups, I'd not have been
> fussed as it could all have been recreated/downloaded so I guess it all
> depends on how important or unique the data is.)
> 
> But if you've got a new machine, why not get new disks and set up a
> nice new clean raid and then just rsync the data accross. That way your
> old disks become the backup, to the data you've newly transfered to
> clean a clean array.
> 
Yup. Do you need the old disks in your new system? If not, DON'T MOVE 
THEM and they'll be your backup.
>>
>> The section 'using the array' has information but I'm not sure how
>> that will work moving from one box to the other.
>>
>> (One question would be if the uuid of the array will remain the same
>> as that would make things easier - - - I could copy the uuid from the
>> existing and then just do the # mdadm --scan --assemble --uuid=
>> blahblah )
>>
Yup. If you move the disks, the UUID won't change.

What I went and did - which took some down-time because it was a pretty 
big array ... was to create my new array on new disks in the new system.

Then I can't remember the syntax - I looked it up on the web - but I 
just did a

cat //old-system/dev/old-array | network > //new-system/dev/newarray

So you're basically copying your filesystem across the network from the 
old "disk" (array, actually) to the new equivalent on the new system.

Worked a treat, apart from the time it took ...

A major reason I went that route, rather than an rsync or whatever, is 
that my system has hard-links all over the place, and while the various 
filesystem copying mechanisms CAN handle it, they don't like it ... a 
device copy simply doesn't need to know anything about it.

Cheers,
Wol

what's wrong with RAID-10? (was "Re: moving a working array")

[David T-G]

Wol, et al --

...and then Wols Lists said...
% 
% On 24/06/2022 15:09, Wilson Jonathan wrote:
% > On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
% > > 
% > > I have a working (no issues) raid-10 array in one box.
% 
% Bummer. It's a raid-10. A raid-1 would have been easier.
[snip]

This tripped me.  I presumed that the reason for -10, not least because
he also said "these 4 drives", was because the array space is bigger than
just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 work
for that storage?  And why would it be easier than RAID-10?


TIA

:-D
-- 
David T-G
See http://justpickone.org/davidtg/email/
See http://justpickone.org/davidtg/tofu.txt

Re: what's wrong with RAID-10? (was "Re: moving a working array")

[Wols Lists]

On 27/06/2022 11:41, David T-G wrote:
> Wol, et al --
> 
> ...and then Wols Lists said...
> %
> % On 24/06/2022 15:09, Wilson Jonathan wrote:
> % > On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
> % > >
> % > > I have a working (no issues) raid-10 array in one box.
> %
> % Bummer. It's a raid-10. A raid-1 would have been easier.
> [snip]
> 
> This tripped me.  I presumed that the reason for -10, not least because
> he also said "these 4 drives", was because the array space is bigger than
> just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 work
> for that storage?  And why would it be easier than RAID-10?
> 
Just that raid-1 would have been a simple case of two drives, each a 
backup of the other. Keep one safe, put the other in the new system.

With raid-10, it's much more complicated - you can't just do that :-(

Cheers,
Wol

Re: what's wrong with RAID-10?

[David T-G]

Wol, et al --

...and then Wols Lists said...
% 
% On 27/06/2022 11:41, David T-G wrote:
% > 
% > ...and then Wols Lists said...
% > %
% > % Bummer. It's a raid-10. A raid-1 would have been easier.
% > [snip]
% > 
...
% > just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 work
% > for that storage?  And why would it be easier than RAID-10?
% > 
% Just that raid-1 would have been a simple case of two drives, each a backup
% of the other. Keep one safe, put the other in the new system.

OH!!  That helps.  I was bummer-ing the wrong aspect and trying to
figure out why RAID-10 was a bad design choice.  Now i get it :-)


% 
% With raid-10, it's much more complicated - you can't just do that :-(

Yeah.


% 
% Cheers,
% Wol


Thanks again!

:-D
-- 
David T-G
See http://justpickone.org/davidtg/email/
See http://justpickone.org/davidtg/tofu.txt

Re: what's wrong with RAID-10? (was "Re: moving a working array")

[Reindl Harald]

Am 27.06.22 um 17:10 schrieb Wols Lists:
> On 27/06/2022 11:41, David T-G wrote:
>> Wol, et al --
>>
>> ...and then Wols Lists said...
>> %
>> % On 24/06/2022 15:09, Wilson Jonathan wrote:
>> % > On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
>> % > >
>> % > > I have a working (no issues) raid-10 array in one box.
>> %
>> % Bummer. It's a raid-10. A raid-1 would have been easier.
>> [snip]
>>
>> This tripped me.  I presumed that the reason for -10, not least because
>> he also said "these 4 drives", was because the array space is bigger than
>> just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 work
>> for that storage?  And why would it be easier than RAID-10?
>>
> Just that raid-1 would have been a simple case of two drives, each a 
> backup of the other. Keep one safe, put the other in the new system.
> 
> With raid-10, it's much more complicated - you can't just do that :-(

you can easily do that with RAID10

* just buy replacement disks
* pull out two disks
* look if it boots
* if not pull a different out
* rebuild the array with the new disks
* put the other two disks with two blank
   ones in the other box
* rebuild the array in the other box
* voila you have two indetical redundant machines

frankly i cloned machines by intention that way

Re: what's wrong with RAID-10? (was "Re: moving a working array")

[Wols Lists]

On 27/06/2022 19:41, Reindl Harald wrote:
> 
> 
> Am 27.06.22 um 17:10 schrieb Wols Lists:
>> On 27/06/2022 11:41, David T-G wrote:
>>> Wol, et al --
>>>
>>> ...and then Wols Lists said...
>>> %
>>> % On 24/06/2022 15:09, Wilson Jonathan wrote:
>>> % > On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
>>> % > >
>>> % > > I have a working (no issues) raid-10 array in one box.
>>> %
>>> % Bummer. It's a raid-10. A raid-1 would have been easier.
>>> [snip]
>>>
>>> This tripped me.  I presumed that the reason for -10, not least because
>>> he also said "these 4 drives", was because the array space is bigger 
>>> than
>>> just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 work
>>> for that storage?  And why would it be easier than RAID-10?
>>>
>> Just that raid-1 would have been a simple case of two drives, each a 
>> backup of the other. Keep one safe, put the other in the new system.
>>
>> With raid-10, it's much more complicated - you can't just do that :-(
> 
> you can easily do that with RAID10

Only if all the disks are the same size ... and an even number ...

Cheers,
Wol

Re: what's wrong with RAID-10? (was "Re: moving a working array")

[Reindl Harald]

Am 27.06.22 um 20:52 schrieb Wols Lists:
> On 27/06/2022 19:41, Reindl Harald wrote:
>>
>>
>> Am 27.06.22 um 17:10 schrieb Wols Lists:
>>> On 27/06/2022 11:41, David T-G wrote:
>>>> Wol, et al --
>>>>
>>>> ...and then Wols Lists said...
>>>> %
>>>> % On 24/06/2022 15:09, Wilson Jonathan wrote:
>>>> % > On Fri, 2022-06-24 at 08:38 -0500, o1bigtenor wrote:
>>>> % > >
>>>> % > > I have a working (no issues) raid-10 array in one box.
>>>> %
>>>> % Bummer. It's a raid-10. A raid-1 would have been easier.
>>>> [snip]
>>>>
>>>> This tripped me.  I presumed that the reason for -10, not least because
>>>> he also said "these 4 drives", was because the array space is bigger 
>>>> than
>>>> just one hard drive size, ie 6T on 4ea 3T drives.  How would RAID-1 
>>>> work
>>>> for that storage?  And why would it be easier than RAID-10?
>>>>
>>> Just that raid-1 would have been a simple case of two drives, each a 
>>> backup of the other. Keep one safe, put the other in the new system.
>>>
>>> With raid-10, it's much more complicated - you can't just do that :-(
>>
>> you can easily do that with RAID10
> 
> Only if all the disks are the same size ... and an even number

in other words: in every typical usecase
how does RAID1 work with different disk sizes?

the point is that "With raid-10, it's much more complicated" is simply 
wrong unledss you say "it can be more complicated if you have a strange 
setup"