[DRBD-user] drbd-user Digest, Vol 119, Issue 24

Allen Chen achen at harbourfrontcentre.com
Fri Jun 27 16:52:17 CEST 2014

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 6/27/2014 6:00 AM, drbd-user-request at lists.linbit.com wrote:
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>     1. Re: drbd-user Digest, Vol 119, Issue 22 (rf at q-leap.de)
> ----------------------------------------------------------------------
> Message: 1
> Date: Fri, 27 Jun 2014 11:12:50 +0200
> From: rf at q-leap.de
> Subject: Re: [DRBD-user] drbd-user Digest, Vol 119, Issue 22
> To: Allen Chen <achen at harbourfrontcentre.com>
> Cc: drbd-user at lists.linbit.com
> Message-ID: <21421.13714.943726.997057 at gargle.gargle.HOWL>
> Content-Type: text/plain; charset=us-ascii
>>>>>> "Allen" == Allen Chen <achen at harbourfrontcentre.com> writes:
>      Allen> Here is my explanation to use DRBD instead of md raid1: for
>      Allen> md raid1, if one member is physically removed from the
>      Allen> machine, and after you reconnect the same disk to md raid1,
>      Allen> MD will re-sync everything to it.
> Wrong, see below.
>      Allen> It takes much more time.  for DRBD, if the second disk is
>      Allen> removed from the machine, and after you reconnect the same
>      Allen> disk to DRBD, DRBD will sync whatever has been changed. It
>      Allen> take less time than MD raid1.
> md raid1 can do the same thing and is definitely the better tool for this
> job. See e.g.
> https://raid.wiki.kernel.org/index.php/Write-intent_bitmap
> Roland
> -------
> http://www.q-leap.com / http://qlustar.com
>            --- HPC / Storage / Cloud Linux Cluster OS ---
I found an interesting feature from DRBD when I test DRBD compered with 
MD raid1.
I am seeking a "relax" disk backup solution. Of cause, both DRBD and 
raid1 can do it.
But I need this feature: if the second node(DRBD) or disk(raid1) is 
offline(no disk errors, no nothing,just disconnected), and comes back 
later, I need the two nodes(DRBD) or disk(raid1) to be synced as soon as 
In this case, DRBD takes a few seconds to sync whatever changed, and 
raid1 takes hours to sync the whole disk(also needs annually add the out 
of sync disk).
So I want to use DRBD to replace raid1 in this case.
Does it have any issue to run DRBD on the same machine?


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