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Re: Raid 1



On Vi, 22 ian 21, 22:26:46, mick crane wrote:
> hello,
> I want to tidy things up as suggested.
> Have one old PC that I'll put 2 disks in and tidy everything up so what's
> scattered about is on the running disks and this new/old one is just backup
> for them.
> Can I assume that Debian installer in some expert mode will sort out the
> raid or do I need to install to one disk and then mirror it manually before
> invoking the raid thing ?

The "raid thing" is a separate layer below the partitions and file 
systems.

Technically it is possible to create the mirror with just one device (I 
believe mdadm calls this "degraded"), partition the md mirror device, 
install, copy data to it, etc., add the second device later and let md 
synchronize the two drives.

Because Linux RAID is a separate layer with no knowledge of the data 
"above" it has to copy every single bit to the other drive as well 
(similar to a dd device-to-device copy), regardless if actually needed 
or not.

If you are really strapped for space and must do this ZFS can do it much 
more efficiently, because it controls the entire "stack" and knows 
exactly which blocks to copy (besides many other advantages over Linux 
RAID).

Unfortunately ZFS is slightly more complicated from the packaging side, 
and installing Debian on a ZFS root is difficult.

It still makes an excelent choice to manage your storage drives, 
especially on a stable system, where there is less hassle with the dkms 
module and it's amazingly simple to use once you familiarise yourself 
with the basics.

Kind regards,
Andrei
-- 
http://wiki.debian.org/FAQsFromDebianUser

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