Re: Snapshots in tmpfs

[Adam Hoka <adam.hoka%gmail.com@localhost>]

On 2/23/2012 7:34 PM, David Young wrote:
> On Thu, Feb 23, 2012 at 07:58:11AM +0000, David Holland wrote:
>> On Wed, Feb 22, 2012 at 08:17:15AM -0600, David Young wrote:
>>  > On Wed, Feb 22, 2012 at 01:42:45PM +0100, Manuel Wiesinger wrote:
>>  > > *)
>>  > > What is it good for? The only practical use I can imagine are
>>  > > backups on thin clients, which operate without a hard disk. But this
>>  > > is clearly far-fetched, in my eyes.
>>  > 
>>  > It's good for writing checkpoints of a tmpfs to non-volatile (NV)
>>  > storage in an embedded system where writing to the NV storage is costly
>>  > (it wears out, or it is slow, or both).  When you have a snapshot, you
>>  > can stream it to NV storage using pax(1).  This is the best practical
>>  > way that I can think of in NetBSD at this time.
>>
>> other than, say, chfs or lfs?
> 
> Is CHFS really suitable for CompactFlash?  Is LFS even usable?

No and no.

> 
>> That sounds like a horrible hack, anyhow, and prone to dying horribly
>> if you crash or lose power in the middle of a writeback. (plus you'd
>> want to use rsync to transfer, or so I'd think, or rewriting
>> unmodified blocks will burn write cycles faster than not bothering to
>> do anything special.)
> 
> I agree that whatever you have in mind sounds like a horrible hack. :-)
> 
> Dave
>