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Re: Reasonably simple setup for 1TB HDD and 250GB M.2 NVMe SSD



Hi.  Thank you for your response.

Em [2021-12-08 qua 14:49:50+0000], piorunz escreveu:

> I understand you have one SATA 2.5" slot in your laptop and one NVMe
> slot, and you want to utilize them both.

That is correct.

>> On the SSD I intend to leave 35 GB unpartitioned for extra over
>> provisioning.  It would have just one 215 GB partition.
>
> Leave more overprovisioning if you can. Use Btrfs with zstd compression
> for your / and /home, you will gain many gigabytes.

How much overprovisioning would you recommend?  I can probably afford
more indeed (because of the 1 TB HDD), but excessive overprovisioning
could increase the risk of the system failing due to lack of disk space
during some important task.  Also, I heard that Linux filesystems like
having some reasonable (some say 10%) internal (within the filesystem)
free space.

> This doesn't make any sense.  Don't run RAID1 SSD+HDD.  You will kill
> all gains SSD NVMe provides.

I lack RAID experience, but I assumed the kernel would easily be smart
enough to read from the fastest RAID member (SSD), so read performance
would be great.  And I hoped the kernel would also be smart enough to,
on writes, write to the SSD first and later (asynchronously) replicate
to the HDD.  But now a quick web search indeed suggests that those
optimizations are not default or common, so we can drop the RAID idea.

> / on NVMe Btrfs
> noatime,nodiratime,space_cache=v2,ssd,compress-force=zstd:6,subvol=@
>
> /home on NVMe Btrfs
> noatime,nodiratime,space_cache=v2,ssd,compress-force=zstd:6,subvol=@home

About those options:

- noatime: I didn't know about this issue, I thought relatime was
  efficient enough.  Thank you for the tip!
- nodiratime: According to the mount manpage, noatime implies
  nodiratime.
- ssd: Does btrfs not autodetect SSD?  Why provide ssd option?
- Why `compress-force' instead of simply `compress'?


For more context, my DE is Gnome and some of my most often used
applications are:

- GNU Emacs
- notmuch and offlineimap (I am considering switching to mbsync)
- GNU IceCat and Mozilla Firefox
- Gajim and GNU Jami
- Nextcloud (it is always running but rarely syncing changes)
- Gnome Boxes or Virtual Machine Manager running a VM with 2 GiB RAM and
  one .qcow2 disk image currently weighting 24 GB.

Kind regards!

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