Re: Lvm think provisioning query

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Does this mean the ext4 is showing wrong information. The file is reported being 90+MB but in actuality the size is less in the FS ?
This is quite ok because it is just that file system being affected. I was however concerned that the file in this FS might have overwritten other LV data since the file is showing bigger than the volume size.

I will try this using BTRFS.


On Fri, Apr 29, 2016 at 10:13 AM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
On 28.4.2016 16:36, Bhasker C V wrote:
Zdenek,
  Thanks. Here I am just filling it up with random data and so I am not
concerned about data integrity
  You are right, I did get page lost during write errors in the kernel

The question however is even after reboot and doing several fsck of the ext4fs
the file size "occupied" is more than the pool size. How is this ?
I agree that data may be corrupted, but there *is* some data and this must be
saved somewhere. Why is this "somewhere" exceeding the pool size ?

Hi

Few key principles -


1. You should always mount extX fs with  errors=remount-ro  (tune2fs,mount)

2. There are few data="" modes ensuring various degree of data integrity,
   An case you really care about data integrity here - switch to 'journal'
   mode at price of lower speed. Default ordered mode might show this.
   (i.e. it's the very same behavior as you would have seen with failing hdd)

3. Do not continue using thin-pool when it's full :)

4. We do miss more configurable policies with thin-pools.
   i.e. do plan to instantiate 'error' target for writes in the case
   pool gets full - so ALL writes will be errored - as of now - writes
   to provisioned blocks may cause further filesystem confusion - that's
   why  'remount-ro' is rather mandatory - xfs is recently being enhanced
   to provide similar logic.



Regards


Zdenek

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