linux-lvm.redhat.com archive mirror
 help / color / mirror / Atom feed
* [linux-lvm] How to handle Bad Block relocation with LVM?
@ 2003-02-10 19:18 Rocky Lee
  2003-02-11  8:24 ` Heinz J . Mauelshagen
  0 siblings, 1 reply; 10+ messages in thread
From: Rocky Lee @ 2003-02-10 19:18 UTC (permalink / raw)
  To: linux-lvm


Hi all

I heard LVM can't not handle  BBR, is that true?

If so,
It maybe a serious problem to me.
is there a trick to handle BBR with LVM + MD?

Thank you if anyone can help to answer these question.

Rocky Lee

^ permalink raw reply	[flat|nested] 10+ messages in thread
* [linux-lvm] Re: How to handle Bad Block relocation with LVM?
@ 2003-02-14  8:52 Eric Hopper
  2003-02-14 11:27 ` Joe Thornber
  0 siblings, 1 reply; 10+ messages in thread
From: Eric Hopper @ 2003-02-14  8:52 UTC (permalink / raw)
  To: linux-lvm

[-- Attachment #1: Type: text/plain, Size: 1816 bytes --]

I manually relocated a few bad blocks on a bad IBM drive I had when I
replaced the drive.  It took a lot of time and effort.  I had to run the
dd command many times very carefully to make it work.

One big problem for me was that read-ahead obscured which actual sectors
were in error.  I needed a 'raw' LVM device, but I don't think such a
thing exists for LVM1 on Linux 2.4.x.

What I did was used pvmove to move the PE containing the bad block to a
different spot on the hard drive, then allocated a new LV that was one
LE long, and forced it to allocate the PE containing the bad block. 
Then I used dd to carefully copy over the LE in sections, narrowing down
the location of the bad sectors until I had copied everything that could
possibly be read.

After that, I ran fsck on the filesystem that had originally contained
the bad block, and I was fine.  I checked carefully, and it didn't even
seem that I had lost any data.

Long, time consuming process though.

Actually, it may have been even ickier than I first thought.

It could be that pvmove wouldn't work, and I had to shorten the LV
containing the bad block (the BLV) to contain all PEs prior to the bad
one, allocate a new LV (the NLV) containing all the bad PE, lengthen the
BLV by 1 PE, using a brand new PE, then lengthen it to its original
length so it would contain all the PEs after that bad PE, the do the
procedure I outlined above.

Now that I think of it, I'm nearly positive that pvmove didn't work.  I
had dearly wished for some kind of option to pvmove that would force it
to try as hard as it could to get good reads of all the sectors in a PE,
then move the LE to a new PE, even if there were errors.

Have fun (if at all possible),
-- 
Eric Hopper <hopper@omnifarious.org>
Omnifarious Software

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 197 bytes --]

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [linux-lvm] How to handle Bad Block relocation with LVM?
@ 2023-03-15 16:00 Roland
  0 siblings, 0 replies; 10+ messages in thread
From: Roland @ 2023-03-15 16:00 UTC (permalink / raw)
  To: linux-lvm

hello,

quite old thread - but damn interesting, though :)

 > Having the PE number, you can easily do
 > pvmove /dev/broken:PE /dev/somewhere-else

does somebody know if it's possible to easily remap a PE with standard
lvm tools,
instead of pvmoving it ?

trying to move data off from defective sectors can need a very long
time, especially
when multiple sectors being affected and if the disks are desktop drives.

let's think of some "re-partitioning" tool which sets up lvm on top of a
disk with bad
sectors and which scans/skips&remaps megabyte sized PE's to some spare
area, before the
disk is being used.  badblock remapping at the os level instead at the
disks controller
level.

yes, most of you will tell it's a bad idea but i have a cabinet full of
disks with bad
sectors and i'd be really be curious how good and how long a zfs raidz
would work on top
of such "badblocks lvm".  at least, i'd like to experiment with that.
let's call it
academical project for learning purpose and for demonstration of lvm
strength :D

such "remapping" could look like this:

# pvs --segments -ovg_name,lv_name,seg_start_pe,seg_size_pe,pvseg_start 
-O pvseg_start -S vg_name=VGloop0
   VG      LV               Start SSize Start
   VGloop0 blocks_good      0     4     0
   VGloop0 blocks_bad       1     1     4
   VGloop0 blocks_good      5   195     5
   VGloop0 blocks_bad       2     1   200
   VGloop0 blocks_good    201   699   201
   VGloop0 blocks_spare     0   120   900
   VGloop0 blocks_good    200     1  1020
   VGloop0 blocks_good      4     1  1021
   VGloop0 blocks_bad       0     1  1022


blocks_good is LV with healty PE's, blocks_bad is LV with bad PE's and
blocks_spare is LV
where you take healthy PE's from as a replacement for bad PE's found in
blocks_good LV

roland
sysadmin


 > linux-lvm] How to handle Bad Block relocation with LVM?
 > Lars Ellenberg lars.ellenberg at linbit.com
 > Thu Nov 29 14:04:01 UTC 2012
 >
 >     Previous message (by thread): [linux-lvm] How to handle Bad Block
relocation with LVM?
 >     Next message (by thread): [linux-lvm] How to handle Bad Block
relocation with LVM?
 >     Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
 >
 > On Thu, Nov 29, 2012 at 07:26:24AM -0500, Brian J. Murrell wrote:
 > > On 12-11-28 08:57 AM, Zdenek Kabelac wrote:
 > > >
 > > > Sorry, no automated tool.
 > >
 > > Pity,
 > >
 > > > You could possibly pvmove separated PEs manually with set of pvmove
 > > > commands.
 > >
 > > So, is the basic premise to just find the PE that is sitting on a bad
 > > block and just pvmove it into an LV created just for the purpose of
 > > holding PEs that are on bad blocks?
 > >
 > > So what happens when I pvmove a PE out of an LV?  I take it LVM moves
 > > the data (or at least tries in this case) on the PE being pvmoved onto
 > > another PE before moving it?
 > >
 > > Oh, but wait.  pvmove (typically) moves PEs between physical volumes.
 > > Can it be used to remap PEs like this?
 >
 > So what do you know?
 > You either know that pysical sector P on some physical disk is broken.
 > Or you know that logical sector L in some logical volume is broken.
 >
 > If you do
 > pvs --unit s --segment -o
vg_name,lv_name,seg_start,seg_size,seg_start_pe,pe_start,seg_pe_ranges
 >
 > That should give you all you need to transform them into each other,
 > and to transform the sector number to PE number.
 >
 > Having the PE number, you can easily do
 > pvmove /dev/broken:PE /dev/somewhere-else
 >
 > Or with alloc anywhere even elsewhere on the same broken disk.
 > # If you don't have an other PV available,
 > # but there are free "healthy" extents on the same PV:
 > # pvmove --alloc anywhere /dev/broken:PE /dev/broken
 > Which would likely not be the smartest idea ;-)
 >
 > You should then create one LV named e.g. "BAD_BLOCKS",
 > which you would create/extend to cover that bad PE,
 > so that won't be re-allocated again later:
 > lvextend VG/BAD_BLOCKS -l +1 /dev/broken:PE
 >
 > Better yet, pvchange -an /dev/broken,
 > so it won't be used for new LVs anymore,
 > and pvmove /dev/broken completely to somewhere else.
 >
 > So much for the theory, how I would try to do this.
 > In case I would do this at all.
 > Which I probably won't, if I had an other PV available.
 >
 >     ;-)
 >
 > I'm unsure how pvmove will handle IO errors, though.
 >
 > > > But I'd strongly recommend to get rid of such broken driver
quickly then
 > > > you loose any more data - IMHO it's the most efficient solution
cost &
 > > > time.
 >
 > Right.
 >
 >     Lars



_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2023-03-15 16:01 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2003-02-10 19:18 [linux-lvm] How to handle Bad Block relocation with LVM? Rocky Lee
2003-02-11  8:24 ` Heinz J . Mauelshagen
2003-02-14  8:52 [linux-lvm] " Eric Hopper
2003-02-14 11:27 ` Joe Thornber
2012-11-28 13:27   ` [linux-lvm] " Brian Murrell
2012-11-28 13:57     ` Zdenek Kabelac
2012-11-29 12:26       ` Brian J. Murrell
2012-11-29 14:04         ` Lars Ellenberg
2012-11-29 22:53           ` Brian J. Murrell
2012-11-29 15:55       ` Stuart D Gathman
2012-11-30  0:10         ` Brian J. Murrell
2023-03-15 16:00 Roland

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).