[DRBD-user] What to do about read errors on the primary?

Alan Robertson alanr at unix.sh
Wed Sep 19 03:42:24 CEST 2012

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

On 09/18/2012 04:37 PM, Arnold Krille wrote:
> Hi,
> On Tuesday 18 September 2012 10:05:31 Alan Robertson wrote:
>> There was another note mentioning backups...
>> DRBD is designed to protect against server and disk failures. Backups
>> primarily protect against human errors, disasters and so on - and I do
>> have backups...
> You called your drbd-setup a backup. Its not a backup and you know it.
I have a separate 3T ESATA removable hard drive I use for backups.  I
can see it from where I sit.   But you apparently know better than I do
what I have in my house.  Quite a remarkable feat from  many thousands
of miles away.

Why do you presume I'm such an idiot?

I know how to recover from backups.   I probably did my first recovery
from backups before you started elementary school.  I've designed,
written, deployed and managed fully automated backup systems - written
disk drivers, SCSI chip drivers, tape drivers, tape jukebox drivers,
file systems, btrees. I've never written disk firmware, but I've written
code at every level above that.  Yeah, I think I know about backups.

I can avoid recovering from backups, since I don't have any data I care
about in the bad blocks.  But I do back up a few times a day at this
point in time ;-)  and I'll back up one more time just before I shut
down to replace the drive (with the replacement that arrived today). 
The fault tolerant dd ideas are more interesting than a simple restore,
since they preserve the bit maps, and inode numbers, are compatible with
the other mirror copy and so on...

I addressed the list so I could learn what DRBD is supposed to do in
these circumstances, to see if I had some settings wrong, and also
suggest what it /could/ do.  A couple of DRBD features came from my
suggestions in the past (as Phillip or Lars could tell you).  Not all my
ideas are equally good, but sometimes they work out.

    Alan Robertson <alanr at unix.sh> - @OSSAlanR

"Openness is the foundation and preservative of friendship...  Let me
claim from you at all times your undisguised opinions." - William

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