Inquiry: disk format change in the future

Inquiry: disk format change in the future

[Yann E. MORIN]

Hello All!

I've searched the archives, but could not find the answer to the
following questions:

 - will there be, or what is the probability of, a disk format change
   in the near future (few months)?

 - if so, what would be the plan for migrating existing file systems
   to the new format?

I'm contemplating using nilfs2 as the file system for my server, as
it offers all the features I need. OTOH, I would be quite disapointed
if migrating my existing file systems to the new format would imply
(too long a) down-time.

Anyway, keep up the very good work! nilfs2 is very nice! :-)

Regards,
Yann E. MORIN.

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Re: Inquiry: disk format change in the future

[Ryusuke Konishi]

(reply added to "Yann E. MORIN")

Hi,
On Wed, 19 Aug 2009 11:31:56 +0200, "Yann E. MORIN" wrote:
> Hello All!
> 
> I've searched the archives, but could not find the answer to the
> following questions:
> 
>  - will there be, or what is the probability of, a disk format change
>    in the near future (few months)?

We still have some possibilities for the format change at this time.

Basically I intend to keep the disk format, but some new features like

- Extended attributes, ACLs
- Rollback
- Checkpoint based remote replication

may require it.  So far, we haven't seen any specific requisition.
 
>  - if so, what would be the plan for migrating existing file systems
>    to the new format?

In that case, I think we should provide a migration tool along with
the change.
 
> I'm contemplating using nilfs2 as the file system for my server, as
> it offers all the features I need. OTOH, I would be quite disapointed
> if migrating my existing file systems to the new format would imply
> (too long a) down-time.

Quite right.  I think it's good if the garbage collector or something
can convert the disk format running background.

> Anyway, keep up the very good work! nilfs2 is very nice! :-)

Thank you!

Ryusuke Konishi

Re: Inquiry: disk format change in the future

[Eric Sandeen]

Ryusuke Konishi wrote:
> (reply added to "Yann E. MORIN")
> 
> Hi,
> On Wed, 19 Aug 2009 11:31:56 +0200, "Yann E. MORIN" wrote:
>> Hello All!
>>
>> I've searched the archives, but could not find the answer to the
>> following questions:
>>
>>  - will there be, or what is the probability of, a disk format change
>>    in the near future (few months)?
> 
> We still have some possibilities for the format change at this time.
> 
> Basically I intend to keep the disk format, but some new features like
> 
> - Extended attributes, ACLs
> - Rollback
> - Checkpoint based remote replication
> 
> may require it.  So far, we haven't seen any specific requisition.
>  

Do you expect that any of the changes may impact the ability of
utilities such as blkid or file to recognize a nilfs filesystem?

I'd happily write patches for those utilities to add nilfs recognition
if you think there is a stable fingerprint that can be recognized.

Thanks,
-Eric

Re: Inquiry: disk format change in the future

[Ryusuke Konishi]

Hi!
On Wed, 19 Aug 2009 22:55:39 -0500, Eric Sandeen wrote:
> Ryusuke Konishi wrote:
> > (reply added to "Yann E. MORIN")
> > 
> > Hi,
> > On Wed, 19 Aug 2009 11:31:56 +0200, "Yann E. MORIN" wrote:
> >> Hello All!
> >>
> >> I've searched the archives, but could not find the answer to the
> >> following questions:
> >>
> >>  - will there be, or what is the probability of, a disk format change
> >>    in the near future (few months)?
> > 
> > We still have some possibilities for the format change at this time.
> > 
> > Basically I intend to keep the disk format, but some new features like
> > 
> > - Extended attributes, ACLs
> > - Rollback
> > - Checkpoint based remote replication
> > 
> > may require it.  So far, we haven't seen any specific requisition.
> >  
> 
> Do you expect that any of the changes may impact the ability of
> utilities such as blkid or file to recognize a nilfs filesystem?

I don't think these affect blkid or similar programs even if
additional fields may be required in the superblock.

One my concern about the automated recognition is too short magic
field of nilfs.  I think those tools will need to confirm the checksum
in addition to the magic field.

If I have a chance to reorganize the superblock, I would like to make
it longer and adjust some other fields.  But I will not do so for the
above features.

> I'd happily write patches for those utilities to add nilfs recognition
> if you think there is a stable fingerprint that can be recognized.
>
> Thanks,
> -Eric

Thank you for the proposal! I'm grateful if you could do so.  I think
the time when we drop the experimental flag from Kconfig is the time.

Thanks,
Ryusuke Konishi

Re: Inquiry: disk format change in the future

[Eric Sandeen]

Ryusuke Konishi wrote:
> Hi!
> On Wed, 19 Aug 2009 22:55:39 -0500, Eric Sandeen wrote:
>> Ryusuke Konishi wrote:
>>> (reply added to "Yann E. MORIN")
>>>
>>> Hi,
>>> On Wed, 19 Aug 2009 11:31:56 +0200, "Yann E. MORIN" wrote:
>>>> Hello All!
>>>>
>>>> I've searched the archives, but could not find the answer to the
>>>> following questions:
>>>>
>>>>  - will there be, or what is the probability of, a disk format change
>>>>    in the near future (few months)?
>>> We still have some possibilities for the format change at this time.
>>>
>>> Basically I intend to keep the disk format, but some new features like
>>>
>>> - Extended attributes, ACLs
>>> - Rollback
>>> - Checkpoint based remote replication
>>>
>>> may require it.  So far, we haven't seen any specific requisition.
>>>  
>> Do you expect that any of the changes may impact the ability of
>> utilities such as blkid or file to recognize a nilfs filesystem?
> 
> I don't think these affect blkid or similar programs even if
> additional fields may be required in the superblock.
> 
> One my concern about the automated recognition is too short magic
> field of nilfs.  I think those tools will need to confirm the checksum
> in addition to the magic field.

That's possible, at least for blkid.  I did that for recognizing lvm
volumes.  I'll take a look.

> If I have a chance to reorganize the superblock, I would like to make
> it longer and adjust some other fields.  But I will not do so for the
> above features.
> 
>> I'd happily write patches for those utilities to add nilfs recognition
>> if you think there is a stable fingerprint that can be recognized.
>>
>> Thanks,
>> -Eric
> 
> Thank you for the proposal! I'm grateful if you could do so.  I think
> the time when we drop the experimental flag from Kconfig is the time.

Ok, I can wait 'til then to submit it.  Once I get time to see what it
takes I can run the patch past you, see if you think it's a stable
fingerprint, and either send it upstream or wait, based on what you
think is best at that point.

Thanks,
-Eric