mksnap_ffs woes

[Andrea Venturoli]

Kris Kennaway wrote:

> mksnap_ffs may sometimes take a long time (order of tens of minutes)
> to generate the snapshot.  During this time, other writes to the
> filesystem may be suspended.  Are you sure this isn't what you're
> seeing?

I am not sure, but I don't think so.

First of all, while I would not expect an exactly deterministic 
behaviour, I still find it strange that most of the times it works 
within seconds, and occasionally it might need so long! Then again, I do 
not have enough insight to explain why it would or why it shouldn't.

I didn't always have the opportunity to check, but I did once: I'm sure 
the disks were not working, and the CPU was not under stress, so I can 
see no reason why it would take that long (I waited for more than an 
hour, then decided to reset).

Lastly, if what you say is true, that "writes to the filesytem may be 
suspended" for that long, then I don't see much point in using this 
feature. At least, it is not one that suits *my* needs: our clients must 
be up 24/7; if that happens they will time out and someone will need to 
go there and powercycle them.

Am I going in the wrong direction then?
Are there other alternatives for live backups?
Is there some sort of more detailed documentation (tutorials, howtos, 
...) on this topic?

  bye & Thanks
	av.