Re: recovering from raid5 corruption

[NeilBrown <neilb@suse.de>]

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On Sun, 29 Apr 2012 19:29:10 -0400 Shaya Potter <spotter@gmail.com> wrote:

> On 04/29/2012 06:52 PM, NeilBrown wrote:
> >
> > You've written a new superblock 4K in to each device, where previously here
> > was something.   So you have probably corrupted something though we cannot
> > easily tell what.
> >
> > Retry your experiment with --metadata=0.90.  Hopefully one of those
> > combinations will work better.  If it does, make a backup of the data you
> > want to keep, then I would suggest rebuilding the array from scratch.
> 
> ok, thanks, that was a huge help.
> 
> I have it setup correctly now (obvious due to the fact that I can read 
> the lvm configuration without any gibberish when ordered correctly).
> 
> however, now I need to figure out how to recreate the lvm appropriately. 
>   I see the configuration "file" in at the start of the raid array (less 
> -f /dev/md0 which I'm including below)
> 
> I asusme there should be a way to reuse this data to recreate the lvm?
> 
> any continued advice would be appreciated, googling doesn't seem to come 
> up with much if one doesn't have a backup of the lvm data.

I don't use LVM myself so I don't know all the details, but doesn't 'pvscan'
find them?  I don't know what you do after that.

NeilBrown


> 
> raid5 {
> id = "8r27WQ-HvIw-0RQV-aksr-LJGN-DLVD-1WBg8h"
> seqno = 6
> status = ["RESIZEABLE", "READ", "WRITE"]
> extent_size = 8192
> max_lv = 0
> max_pv = 0
> 
> physical_volumes {
> 
> pv0 {
> id = "7P0W3p-XoPg-rCo8-HJ2G-Hfxc-UDWI-x6nQck"
> device = "/dev/md0"
> 
> status = ["ALLOCATABLE"]
> dev_size = 11721107456
> pe_start = 384
> pe_count = 1430799
> }
> }
> 
> logical_volumes {
> 
> data {
> id = "YZvrHt-Glyr-wnj0-QzV1-qRe6-VcRH-D7wU3U"
> status = ["READ", "WRITE", "VISIBLE"]
> segment_count = 1
> 
> segment1 {
> start_extent = 0
> extent_count = 524288
> 
> type = "striped"
> stripe_count = 1        # linear
> 
> stripes = [
> "pv0", 0
> ]
> }
> }
> 
> image {
> id = "uHOzpc-l8L7-eF5h-Fa0C-EsCS-sM6X-3GpOP0"
> status = ["READ", "WRITE", "VISIBLE"]
> segment_count = 1
> 
> segment1 {
> start_extent = 0
> extent_count = 906511
> 
> type = "striped"
> stripe_count = 1        # linear
> stripes = [
> "pv0", 524288
> ]
> }
> }
> }
> }
> # Generated by LVM2 version 2.02.39 (2008-06-27): Wed Aug 19 23:36:50 2009
> 
> contents = "Text Format Volume Group"
> version = 1
> 
> description = ""
> 
> creation_host = "nas"   # Linux nas 2.6.27-14-generic #1 SMP Fri Jul 24 
> 22:19:33 UTC 2009 i686
> creation_time = 1250739410      # Wed Aug 19 23:36:50 2009


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