linux-lvm.redhat.com archive mirror
 help / color / mirror / Atom feed
From: Marc Weber <marco-oweber@gmx.de>
To: linux-lvm@redhat.com
Subject: Re: [linux-lvm] RAID1 mirroring behavior when one disk is dead sometimes - why not just use random numbers ??
Date: Thu, 15 Apr 2021 06:19:50 +0200	[thread overview]
Message-ID: <9a08e0e2-2423-c7f2-df96-94caf53eb0b3@gmx.de> (raw)
In-Reply-To: <CAP1D0fRH2Ngk-1pVdTcVRiGcXtyW=JJ2c9Tj3Bk0LGG7neZWkg@mail.gmail.com>


> As far as I know mdadm works the same way. (At least it was working
> like this when this thread happened:
> https://www.spinics.net/lists/raid/msg36962.html)
>
> You can use a similar tactic that was recommended there: Don't
> assemble a degraded RAID1 array without user interaction. You can do
> this by changing the activation mode to complete in lvm.conf.

But then the server doesn't start at all which might also be costly.


The thread says that clock i not reliable eventually due to faulty hardware etc.

*BUT* why isn't there a way to 'stamp' the disks once clock is synced with the internet ?


Let's compare two cases and two solutions.


solution 1:

write dates [date, known-devices] to the active disks

CASE: disk 1 appears sometimes. disk2 would have 'know-devices' disk2 only, so disk1 could be identified as troublesome.

action mirror disk2  to1


CASE: split brain: disk1 appears, reboot disk2 appears, reboot both appear

Dates would be different. -> no mount


Not using the date info at all, thus could be using random numbers which would be solution 2.



I don't have experience how often disks appear sometimes only.

To me it looks like having such strategy above which also could be implemented in user space (but why ?)

would work in more cases very well cause the server would boot more often than not.


Marc Weber


_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

      reply	other threads:[~2021-04-15  4:20 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-13 15:52 [linux-lvm] RAID1 mirroring behavior when one disk is dead sometimes? Marc Weber
2021-04-13 19:44 ` Péter Sárközi
2021-04-15  4:19   ` Marc Weber [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9a08e0e2-2423-c7f2-df96-94caf53eb0b3@gmx.de \
    --to=marco-oweber@gmx.de \
    --cc=linux-lvm@redhat.com \
    --subject='Re: [linux-lvm] RAID1 mirroring behavior when one disk is dead sometimes - why not just use random numbers ??' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).