[mdlug] Damaged Image recovery

[Michael Mikowski]

I've been using Software RAID level 1 on Linux for about 10 years.  Its a very solid solution -- the load on the system is virtually nill, and reads are faster (writes are about the same speed, IIRC).  Look for 'mdadm' for setting it up.

The disk topology I've used is:

1 SATA System Disk
2 SATA Data Disks

The data disks are exactly the same capacity and model.  Then I create 1 or 2 partitions on each and create RAID devices (again, see mdadm).  I mount data I care about on the RAID devices, e.g. /home.  Any system settings in /etc can be backed up to the RAID through a cronjob rsync.


>From my research, it appears that software RAID is faster and more reliable than 'Fake RAID' that you get when you try to use a psuedo-RAID motherboard.  So if you have one of those MOBO's, I'd recommend turning 'RAID' OFF in the bios and going to straight software RAID.  I've done that with my current workstation/server, and it works great.

About rsync: It has its place (see the /etc note above), and I have never seen data corruption with it over many years of use.

And SATA RAID almost certainly beats the pants off USB drives for performance and reliability :)

Cheers, Mike



----- Original Message ----
From: Robert Adkins <radkins at impelind.com>
To: MDLUG's Main discussion list <mdlug at mdlug.org>
Sent: Friday, September 25, 2009 2:01:19 PM
Subject: Re: [mdlug] Damaged Image recovery

In the future, you might want to look at the Linux Kernel controlled RAID
setup.

>From what I have read on it, you can create a software RAID controlled by
the Linux Kernel which will provide the mirroring you are seeking, without
the potential issues/trouble of rsync. As I understand it, the solution is
rather solid.

If you are upgrading your system, you could always look into a
motherboard/case combination that will allow you to put an External SATA
drive on your system. Then you can create a RAID 1 mirror with an internal
and the external drive and provide yourself with that hard drive failure
protection and quick/ease of grabbing/running if something untoward happens
to your domicile.

-Rob


> -----Original Message-----
> From: mdlug-bounces at mdlug.org 
> [mailto:mdlug-bounces at mdlug.org] On Behalf Of David McMillan
> Sent: Friday, September 25, 2009 4:26 PM
> To: MDLUG's Main discussion list
> Subject: [mdlug] Damaged Image recovery
> 
> 
>     So, in my ongoing saga of failing hard drives (which is 
> still ongoing) I finally looked at what data *did* det 
> rsync'd before the source drive hit the floor.  And found 
> that, out of my collection of thousands of pictures and 
> photos (mostly JPGs), I've had a nearly 40% loss rate.  The 
> files are still there, and seem to be roughly the right size, 
> but image-viewing applications just show them as dimensioned 
> 0x0 pixels.
>     Does rsync have a history of messing up image files?  I 
> *know* that
> (almost?) all of these corrupted images were good *before* 
> they were rsync'd to the backup mirror.
>     Anyway, *now* I need a good tool for doing mass 
> recovery of corrupted image files.  Since they were all 
> corrupted at the same time, my guess is whatever happened, it 
> happened the same to all of them.  So if I can determine what 
> happened, maybe I stand a chance of undoing it.
>     Recs, anyone?  I've already ruled out moving to the 
> back country of New Zealand and starting a technology-free 
> fully-organic subsistence farm (technology just *hates* me 
> this month....)
> 
> 
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