al3xu5 via Dng said on Sun, 18 Jun 2023 13:24:14 +0200

>Hi all
>
>I apologize if I'm OT... but I would like advice from you.
>
>My current system derives from a migration from Debian to Devuan
>carried out since the "origins", even before Jessie, then updated over
>the years to Chimaera.
>
>The system is installed on a WD Velociraptor 250GB 10000rpm,
>with Power_On_Hours of over 10000 Hours. Other info: LXDE Desktop, RAM
>32GB.
>
>I am considering replacing the system disk with an SSD SATA SAMSUNG
>870EVO 500GB (1.5 Million Hours MTBF) on which to proceed with a fresh
>installation of Daedalus.
>
>There is also a second mechanical disk (MDM RAID: 2x 1TB mirrored)
>whose partitions are mounted on /media.
>
>I also have an external backup of the WHOLE system ;-)
>
>The basic idea is to use the SSD disk for the system, moving the
>partitions (or directories) on which the most writes take place to the
>mechanical disk, also by accepting a compromise between speed and
>duration of the SSD disk.

The preceding paragraph is what I've been doing for years. The root
partition on an NVMe SSD, and all my changing data on spinning rust.

>
>For this I would like to know your opinions and suggestions.
>
>Currently:
>

>$ lsblk
>NAME    MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
>sda       8:0    0 232,9G  0 disk  
>├─sda1    8:1    0  46,6G  0 part  /
>├─sda2    8:2    0  93,1G  0 part  /home

/home belongs on your sdc drive. There might be arguments for putting
either/or /tmp, /var and/or [swap] on spinning rust, as they get
written to A LOT. Most computers have /tmp as a tmpfs that exists only
in RAM and isn't persistent.

>├─sda3    8:3    0     1K  0 part  
>├─sda5    8:5    0  55,9G  0 part  /tmp
>├─sda6    8:6    0  18,6G  0 part  /var
>└─sda7    8:7    0  14,9G  0 part  [SWAP]
>...
>sdc       8:32   0 932G  0 disk  
>├─sdc1    8:33   0 233G  0 part  
>│ └─md1   9:1    0 233G  0 raid1 /media/DATA
>├─sdc2    8:34   0 275G  0 part  
>│ └─md2   9:2    0 275G  0 raid1 /media/MISC
>├─sdc3    8:35   0 275G  0 part  
>│ └─md3   9:3    0 275G  0 raid1 /media/SOFTWARE
>└─sdc4    8:36   0 138G  0 part  
>  └─md4   9:4    0 138G  0 raid1 /media/VM

>
>My hypothesis is:
>

>- system disk (SSD 500GB):
>TYPE    SIZE    MOUNTPOINT
>part     50G    /       
>part     50G    /home   
>part    200G    /media/VM <-- moved from sdc disk
>        200G    [unused]
>- other mechanical disk
>TYPE    SIZE    MOUNTPOINT
>...
>part     60G    /tmp  
>part     20G    /var
>part     16G    [SWAP]

Why is /tmp so big?
>...
>- using symbolic links: "move" /home/desktop and
>/home/downloads to /media/DATA (on the sdc mirrored disk)

Do you mean bind mounts?

>
>
>The first big question is: is it still appropriate, with current SSD
>discs, try to reduce writings?

Yes. Not nearly as important as in the past, but still a good idea for
letting SSDs live a long and happy life. Also, SSDs shouldn't, in my
opinion, get over 50% full.

>
>And then: which mechanical disk should be used for /tmp, /var, swap
>etc...? Better reuse the "old" non-raid system disk (WD 10000rpm), or
>the actual mirrored sdc disk (see above)?

You don't say how big the mirrored disk is, but if it's a dinky 1TB
like your 10000rpm I'd advise buying a new disk that holds at least
8TB, and 12, 14, or 16TB would be any better.

>Other doubts are:
>- Is it worth bringing with symbolic links /home/desktop and
> /home/downloads on the mechanical mirrored disk (sdc)?

I'd put the entire /home partition on the spinning rust.

>- About /var: could I limit myself to "move" using symbolic links only
> /var/log, /var/mail, /var/spool, /var/tmp?

By the time you do that, why not just put all of /var on the spinning
rust?

>- Does this complexity risk leading to an unstable or fragile system?

It sure hasn't for me. But I use bind mounts, not symlinks.

>- Is this complexity justified compared to the longer duration of the
>SSD disc?

I don't see it as that complex, and if you use your disks hard, I'd
call it justified.

>- What else I'm not considering and/or evaluating?

Friends don't let friends use Seagate drives. I recommend Western
Digital.


SteveT

Steve Litt
Autumn 2022 featured book: Thriving in Tough Times
http://www.troubleshooters.com/bookstore/thrive.htm