NetBSD - Live Network Backup

dvl writes "It is possible but inconvenient to manually clone a hard disk drive remotely, using dd and netcat. der Mouse, a Montreal-based NetBSD developer, has developed tools that allow for automated, remote partition-level cloning to occur automatically on an opportunistic basis. A high-level description of the system has been posted at KernelTrap. This facility can be used to maintain complete duplicates of remote client laptop drives to a server system. This network mirroring facility will be presented at BSDCAN 2005 in Ottawa, ON on May 13-15."

Comments

Pros and Cons

[teiresias]

This would be an extremely sensitive server system. With everyones harddrive image just waiting to be blasted to a blank harddrive, the potential for misdeeds is staggering. Even in an offical capacity, I really feel uneasy if my boss was able to take a copy of my harddrive image and see what I've been working on. Admittely, yes it should all be work but here we are allowed a certain amount of freedom with our laptops and I wouldn't want to have that data at my bosses fingertips.

On the flipside, this would be a boon to company network admins especially with employees at remote sites who have a hard crash.

Another reason to build a high speed backbone. Getting my 80GB harddrive image from Seattle, while I'm in Norfolk would be a lot of downtime.

How long before this becomes a hack?

[Bret Tobey]

Assuming you can get around bandwidth monitoring, how long before this becomes incorporated into hacking tools. Add this to a little spyware and a zombie network and things get very interesting for poorly secured networks & computers.

Done this for years

[OutOfMemory]

I've been using der Mouse to copy files for years. First I user der Mouse to click on the file, then I use der Mouse to drag it to a new location!

Re:use rsync

[FreeLinux]

This is a block level operation, whereas rsync is file level. With this system you can restore the disk image including partitions. Restoring from rsync would require you to create the partition, format the partition and the restore the files. Also, if you need the MBR...

As the article says, this is drive imaging whereas rsync is file copying.

Re:Right solution, wrong problem

[gordon_schumway]

I'd like a system library that would modify the rename(2), truncate(2), unlink(2), and write(2) calls to move the deleted stuff to some private directory (/.Trash, /.Recycler, whatever). Obviously the underlying routine would have to do its own garhage collection, deleting trash files by some FIFO or largest-older-first algorithm.

Done.

WTF

[multipartmixed]

Why on earth are people always so insistent on doing raw-level dupes of disks?

First of all, it means backing up a 40GB with 2 GB of data may actually take 40GB of bandwidth.

Second of all, it means the disk geometries have to be compatible.

Then, I have to wonder if there will be any wackiness with things like journals if you're only restoring a data drive and the kernel versions are different...

I have been using ufsdump / ufsrestore on UNIX for ...decades!. It works great, and its trivial to pump over ssh:

# ssh user@machine ufsdump 0f - /dev/rdsk/c0t0d0s0 | (cd /newdisk && ufsrestore f -)

or


# ufsdump 0f - /dev/rdsk/c0t0d0s0 | ssh user@machine 'cd /newdisk && ufsrestore 0f -' .. it even supports incremental dumps (see: "dump level"), which is the main reason to use it over tar (tar can to incremental with find . -newer X | tar -cf filename -T -, but it won't handle deletes).

So -- WHY are you people so keen on bit-level dumps? Forensics? That doesn't seem to be what the folks above are commenting on.

Is it just that open source UNIX derivative and clones don't have dump/restore utilities?

The Dark Side of Image Backups

[RonBurk]

Image backups have great attraction. Restoring is done in one big whack, without having to deal with individual applications. Absolutely everything is backed up, so no worries about missing an individual file. etc. So why haven't image backups replaced all other forms of backup? The reason is the long list of drawbacks.

• All your eggs are in one basket. If a single bit of your backup is wrong, then the restore could be screwed -- perhaps in subtle ways that you won't notice until it's too late to undo the damage.
• Absolutely everything is backed up. If you've been root kitted, then that's backed up too. If you just destroyed a crucial file prior to the image backup, then that will be missing in the restore.
• You really need the partition to be "dead" (unmounted) while it's being backed up. Beware solutions that claim to do "hot" image backups! It is not possible, in the general case, for a backup utility to handle the problem of data consistency. E.g., your application stores some configuration information on disk that happens to require two disk writes. The "hot" image backup software happens to backup the state of the disk after the first write, but before the second. If you then do an install, the disk is corrupted as far as that application is concerned. How many of your applications are paranoid enough to survive arbitrary disk corruption gracefully?
• Size versus speed. Look at the curve of how fast disks are getting bigger. Then look at the curve of how fast disk transfer speeds are getting faster. As Jim Gray says, disks are starting to behave more like serial devices. If you've got a 200GB disk to image and you want to keep your backup window down to an hour, you're out of luck.
• Lack of versioning. Most disk image backups don't offer versioning, certainly not at the file level. Yet that is perhaps the most common need for a backup -- I just messed up this file and would like to get yesterday's version back, preferably in a few seconds by just pointing and clicking.
• Decreased testing. If you're using a versioned form of file backup, you probably get to test it on a fairly regular basis, as people restore accidental file deletions and the like. How often will you get to test your image backup this month? Then how much confidence can you have that the restore process will work when you really need it?

Image backups certainly have their place for people who can understand their limitations. However, a good, automatic, versioning file backup is almost certainly a higher priority for most computer users. And under some circumstances, they might also want to go with RAID for home computers.