Author Topic: Could you explain the "Reconcile" command and the "Forced-Sync"  (Read 2745 times)

Offline vletroye

  • Hero Member
  • *****
  • Posts: 714
  • Karma: +7/-0
    • View Profile
Could you explain the "Reconcile" command and the "Forced-Sync"
« on: February 07, 2013, 02:13:41 pm »
The best help I found about the various commands available in the WebUI is actually in this post:http://wiki.flexraid.com/2011/10/12/command-execute/

I still have however some questions:

1) Force-Sync-Verify: validates the RAID configuration and synchronizes any bit mismatch to the parity data

So, this is detecting data changed on the DRU but not yet "reflected" into the PPU and recompute the parity for those data, right ? This task must be as long as the RAID initialization I presume, as it has to recompute the parity for the whole content of the DRUs in order to compare with the PPU's ?


2) Reconcile: Reconciles the filesystem databases of a Real-Time RAID configuration with the underlying filesystem

It's mentioned in other posts that the filesystem databases have better be backuped regularly for the purpose of "Reconcile".

I read also that a "Reconcile" may be done:
- after a crash of the server
- after editing data on a disk outside of the Pool (edits that are obviously not recommended)

I don't understand however the purpose of the filesystem databases ? How are they related to the PPU ?
And may I understand that a "Reconcile" is a kind of recovery of corrupted files (datarots ?) on the DRU ?


 3) How do we know that we must do a Reconcile or a Forced-Sync ? I.e.: is it a file which is corrupted or the PPU which is not up-to-date...
« Last Edit: February 07, 2013, 02:43:24 pm by vletroye »

Offline Brahim

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,547
  • Karma: +204/-16
    • View Profile
Re: Could you explain the "Reconcile" command and the "Forced-Sync"
« Reply #1 on: February 07, 2013, 02:50:36 pm »
I don't see two questions.  :P

So, to your one question, RT RAID creates its own light weight filesystem database on top of your existing filesystem.
That database is automatically backed up when you make structural changes to your RAID or after you Create and Verify it.
You can take additional backups too after you've done a lot of activities on the pool.

The backup is used almost as restore point from which RT RAID will re-sync itself.
Whenever, you get a reconcile error, you have to restore the DBs from backup and run the Reconcile task.
If the run fails, you need to delete that backup as it is invalid and restore a backup prior.
You have to do this until Reconcile works.

Typically, users should restore the backup prior to the last for Reconcile to work.
Restoring the very last backup in some cases will still fail the Reconcile task.

Restoring the RT RAID backups and running Reconcile is just part of running RT RAID.

Offline vletroye

  • Hero Member
  • *****
  • Posts: 714
  • Karma: +7/-0
    • View Profile
Re: Could you explain the "Reconcile" command and the "Forced-Sync"
« Reply #2 on: February 07, 2013, 02:59:59 pm »
I did click on "Post" by accident before adding the other questions...

Thx for this first answer !
So, opposite to my understanding, a "Reconcile" does not touch the data on the DRU...

Offline Brahim

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,547
  • Karma: +204/-16
    • View Profile
Re: Could you explain the "Reconcile" command and the "Forced-Sync"
« Reply #3 on: February 07, 2013, 11:02:24 pm »
FlexRAID never change your data unless you are writing through the pool.

Do not use Verify Sync if the RAID is out of sync.
It just overrides the parity and trusts the data as valid even in the case of datarot.

Offline vletroye

  • Hero Member
  • *****
  • Posts: 714
  • Karma: +7/-0
    • View Profile
Re: Could you explain the "Reconcile" command and the "Forced-Sync"
« Reply #4 on: February 08, 2013, 12:03:00 am »
Ok.

So, when there are issues resulting in DRUs and PPUs being out-of-sync

1) Always try first to restore the FR filesystem databases (not to be confused with the FR Configuration database) and a reconcile.

2) Next , if the issues persist, try a "Forced-Sync Verify" as far as DRUs are 100% sure healthy.

3) Then, if not yet fixed, do a Recreate.

4) Finally, if still in troubles,
 a) delete the FR Configuration,
 b) check that VSS is not enabled with its Storage on the PPU/DRU,
 c) check that System account is granted full control on the disks,
 d) check that "Recycle Bin's" are not enabled on PPU/DRU, and recreate the FR Configuration
 e) possibly create a dummy file c:\WHS.FlexRAID for WHS servers (2003 WHS or 2012 Essentials)

Valid ?
« Last Edit: February 08, 2013, 11:18:37 am by vletroye »

Offline Brahim

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,547
  • Karma: +204/-16
    • View Profile
Re: Could you explain the "Reconcile" command and the "Forced-Sync"
« Reply #5 on: February 08, 2013, 11:14:38 am »
Correct.

Online vestige

  • Hero Member
  • *****
  • Posts: 3,567
  • Karma: +0/-0
    • View Profile