[list] [ale] Need advice on home back-up solution

[Greg Freemyer]

On Mon, 2003-09-29 at 10:21, Jonathan Glass wrote:
> On Sun, 2003-09-28 at 16:28, David Corbin wrote:
> > On Sunday 28 September 2003 16:14, Geoffrey wrote:
> > > Greg wrote:
> > > First of all, that sounds like a big pain in the ass. :)  
> > 
> > It is unfortuntate that you have to power down to swap drives, but it's not 
> > the end of the world.
> 
> Actually, if you're willing to spend some money, you can get hot-swappable IDE drives by purchasing a suitable IDE RAID card.
> I use the following at home and at work.
> http://www.promise.com/product/product_detail_eng.asp?productId=8&familyId=2
> 
> I haven't actually TRIED the hot-swap feature, but now that I'm mentioning it, I'd better test it..darned Murphy!.  :)
> 
> Thanks
> 
> Jonathan Glass
It works, but you have to be sure you do it right, you can not just pull
the drive.  

FYI: I use XFS as my filesystem.  It comes with a command xfs_freeze.

First, you have to ensure that write cache is disabled in both the
controller and in the drive.

Given that I normally do a "sync; xfs_freeze -f" then pull the drive.

After it is pulled, I do a xfs_freeze -u (-u = unfreeze).

The xfs_freeze command ensures that the Linux cache is written to disk
and that the journal is set to a consistent state.  Then is stops all
further disk i/o.

The unfreeze allows disk i/o to resume.

I think most of the major Linux Filesystems have similar commands.

FYI: This type of freeze is required by LVM prior to it making a
snapshot.

Greg