Re: recovering from raid5 corruption

[Shaya Potter <spotter@gmail.com>]

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.

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