[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.
Fine.
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
Wilberforce

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