Re: Recovery on new 2TB disk: finish=7248.4min (raid1)

[Roman Mamedov <rm@romanrm.net>]

On Sun, 30 Apr 2017 13:04:36 +0100
Nix <nix@esperi.org.uk> wrote:

> Aside: the storage server I've just set up has a different rationale for
> having multiple mds. There's one in the 'fast part' of the rotating
> rust, and one in the 'slow part' (for big archival stuff that is rarely
> written to); the slow one has an LVM PV directly atop it, but the fast
> one has a bcache and then an LVM PV built atop that. The fast disk also
> has an md journal on SSD. Both are joined into one LVM VG. (The
> filesystem journals on the fast part are also on the SSD.)

It's not like the difference between the so called "fast" and "slow" parts is
100- or even 10-fold. Just SSD-cache the entire thing (I prefer lvmcache not
bcache) and go.

> So I have a chunk of 'slow space' for things like ISOs and video files
> that are rarely written to (so a RAID journal is needless) and never
> want to be SSD-cached, and another (bigger) chunk of space for
> everything else, SSD-cached for speed and RAID-journalled for powerfail
> integrity.
> 
> (... actually it's more complex than that: there is *also* a RAID-0
> containing an ext4 sans filesystem journal at the start of the disk for
> transient stuff like build trees that are easily regenerated, rarely
> needed more than once, and where journalling the writes or caching the
> reads on SSD is a total waste of SSD lifespan. If *that* gets corrupted,
> the boot machinery simply re-mkfses it.)

You have too much time on your hands if you have nothing better to do than
to babysit all that b/s.

-- 
With respect,
Roman