Didier Kryn - 05.12.23, 10:12:01 CET:
> Le 05/12/2023 à 09:09, Martin Steigerwald a écrit :
> > terryc - 05.12.23, 04:18:40 CET:
[…]

>      Congrats Martin; you seem to have some expertise in filesystems and
> how to trim them. Unfortunately this isn't very common, and not my
> case :~). I used to always specify the noatime option, because I have no 
> application relying on file access time. Have you any such application 
> installed?

Not that I am aware of, but I still decided I like to have some estimate
on last access (the usually default relatime) on my laptops, on servers I
sometimes use noatime.

>      I noticed your sysctl command, which, I guess, sets the lifetime of
> data in the VFS buffers before they are actually written to disk. It
> is also available in /proc/sys/vm/dirtytime_expire_seconds and is set
> to 43200 in my laptop. What is the goal of reducing it to 7200?

Read about lazytime mount option, for example in manpage mount(8). It is
all explained there. The option just changes the default of 24 hours - 24
* 60 * 60 = 86400 seconds, maybe it has been changed to 12 hours i.e.
43200 seconds meanwhile or did you change the option yourself? - when
inode is written out *just* for time updates in case there has been no
other reason to write it out before. I do not like to have time out of
date by up to 24 hours in case of a sudden shutdown, but 2 hours is what I
easily tolerate.

It is not related in any way to writing out data that is written to files
on a filesystem. I changed some options there as well but that was not the
topic here.

>      What does mean the line "Percentage Used: 1%" in your diagnostic 
> listing? Cause if only 1% of the disk is used, it should last longer 
> than if 99% was used, but not many people can afford disks 100 time 
> bigger than their storage need.

Did you read what I quoted!? It is about usable *life time* of an SSD.
Life time != storage capacity! 1% means that 1% of usable lifetime by
estimation of the vendor has been used up. This value does not indicate
anything about the storage capacity of the SSD and how much of the storage
capacity has been used.

The only relation is: If you keep more storage capacity free, unused, then
the SSD will have a longer usable lifetime.

Also I wrote about, if you can, let 10-20% of capacity unused, not 99%.

Please really read what I wrote. I don't think it has been that unclear.

> You also talk about the noise of a monster spinning disk used for
> backup, but the recommendation for a backup disk is to *not* let it
> powered all the time. I've read that a spinning disk used rarely is
> considered the most resilient backup storage, in contradiction with SSDs
> which loose data if they aren' t periodically powered.

Steve talked about using a monster spinning disk in his mail not for
backup purposes, but for example for "/var" and "/home" I think, I bet for
his workstation. My comment was related to that. I would not tolerate such
a disk in my workstation nowadays anymore I bet.

I use Toshiba Canvio 4TB disks for backup and these spin down after a few
minutes of not being used.

Ciao,
--
Martin