(Re ** 6)[1]: Extending "thin_trim" (about pseudo-raid: Why!)

(Re ** 6)[1]: Extending "thin_trim" (about pseudo-raid: Why!)

["Thomas Brücker"]

Dear Mr. Kabelac,

* I have had two (real!) cases which three mechanical harddisks, that have
had defective sectors (within warranty time!), not just announced as
defective, but really unreadable.

1st case: Two ecolocical, energy saving samsung disks, that have both got
unreadable sectors, happyly mutually not on the same location, connected
as raid1: All data could be read and saved.

2nd case: An usb-disk that had got unreadable sectors with a 'pseudo-raid'
on it: All data could be read and saved.

* Experimental case: Test of 'pseudo-raid' on a dvd, the dvd was scratched
and could partially not be read: The pseudo raid could be read without any
problem (
* ok. if the metadata on the dvd, which is responsible to have access to
  the dvd at all, is scratched, you loose everything.
* about a read-only!-dvd with 'raid' on it ...: I use another 'strange'
  construct with dm-target dm-snapshot to protect the dvd from writing to.
).

* I have had at least two (real) cases of harddisks with each having a
unreadable first sector (== the partition table): The laptops could
neither
been started, nor could the data.been accessed, After rewriting the
partition table, the disks worked just long enough, to copy a complete
image of them.
(either the disk has a partiton at the 'usual' location, or you may search
for the begin of the filesystem...)

* Link (I don't want to attach and clutter your mail server with unneces-
  sary images) to: Defective disk in harddisk device.
  "http://www.thomas-r-bruecker.ch/favorites/io/disk/Defective_disk.jpg".
  (It begins mostly with defective sectors and ends in a crash.)

* So, for me, it is a good idea, to protect myself from defective sectors.

* 'Normal' raid(1):
  * notebooks with two harddisks in it ...?
  * travelling with a laptop and two usb-harddisks ...?


Sincerely

Thomas

============================================================================
On Tue, November 19, 2024 2:37 pm, Zdenek Kabelac wrote:
> Dne 19. 11. 24 v 3:11 "Thomas Bruecker" napsal(a):
>> ]...]

> [...]
> And while I can 'see' a small value in having the same data stored
> multiple times on the same drive - the protection you get from this is
> close to nothing
> [...]
> With prices of storage these days I'd simply recommend to simply use the
> raid the way it's supposed to be used.
> [...]

Re: (Re ** 6)[1]: Extending "thin_trim" (about pseudo-raid: Why!)

[Zdenek Kabelac]

Dne 20. 11. 24 v 2:28 "Thomas Brücker" napsal(a):
> Dear Mr. Kabelac,
>
> * I have had two (real!) cases which three mechanical harddisks, that have
> had defective sectors (within warranty time!), not just announced as
> defective, but really unreadable.
>
> 1st case: Two ecolocical, energy saving samsung disks, that have both got
> unreadable sectors, happyly mutually not on the same location, connected
> as raid1: All data could be read and saved.
>
> 2nd case: An usb-disk that had got unreadable sectors with a 'pseudo-raid'
> on it: All data could be read and saved.


Hi


Any device that is showing  'error' sectors (aka  smartctl shows badblocks, 
uncorrectable errors)   should be ASAP 'recovered/copied' to another new disk 
- and such faulty disk should no longer be used for anything you care about!

If you think  the disk is still 'good enough' to not be thrown to 
trash/recycle bin -  you could probably do a surface analysis - and i.e. 
allocate partitions on a drive in such a way that HUGE portion of drive before 
and after the error  is left  as not being used/allocated   (works for HDD -   
for SSD/NVMe this obviously makes no sense) -  so then HDD reading heads are 
not damaging those errori places any more - and then you can try to use it to 
store something unimportant - i.e.  3rd. backup of something....

Using faulty drive as 'daily work  disk'  with the idea you've 'saved' 
something  makes no sense - you are just preparing yourself big troubles....


> * Experimental case: Test of 'pseudo-raid' on a dvd, the dvd was scratched
> and could partially not be read: The pseudo raid could be read without any
> problem (


Just backup all your DVDs on TiB drives  while they are still readable....


>
> * I have had at least two (real) cases of harddisks with each having a
> unreadable first sector (== the partition table): The laptops could
> neither

Such drives are simply an electronic waste for recycling...


> * So, for me, it is a good idea, to protect myself from defective sectors.
>
> * 'Normal' raid(1):
>    * notebooks with two harddisks in it ...?
>    * travelling with a laptop and two usb-harddisks ...?


Seriously you should really use real  raid1 instead of these rather highly 
'questionable' data protection ideas...  (if you care about your data)

And yes - all notebooks I know  have at least  2 slots for drives - one is 
typically equipped when being sold - other one is usually empty - one just has 
to dismount laptop cover and add the drive to unused slot...


Regards

Zdenek