Re: raid-5 initiated as raid-4?

[Roy Sigurd Karlsbakk <roy@karlsbakk.net>]

> > root@raidtest:~# cat /proc/mdstat
> > Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
> > [raid4] [raid10]
> > md0 : active raid5 vdf[5](S) vde[4](S) vdd[3] vdc[1] vdb[0]
> >       4191232 blocks super 1.2 level 5, 512k chunk, algorithm 2
> >       [3/3] [UUU]
> 
> Where did vde & vdf spring from? They weren't in your create command -
> did you add those as spares later?

Yes

>
> > Does this mean the raid-5 is actually initiated as a raid-4?
> >
> RAID-5 is always created with n-1 disks, with the final disk being
> recovered afterwards. It's quicker to do a linear read from the other
> disks and a linear write onto the final disk (creating parity or
> rebuilding the data as needed) than it is to intersperse reads &
> writes
> on all disks and just create the parity data (for RAID5 anyway -
> reconstructing the data on a RAID6 from P & Q parity is far more
> expensive, so it's quicker to just generate the parity there).

ok, so do I understand correctly that the initial raid-5 build only writes data/parity to a single drive (the 'replacement')? Doing some more testing now to see what I can find…

Vennlige hilsener / Best regards

roy
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Roy Sigurd Karlsbakk
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