Re: RAIDING different size drives

Rod Speed wrote:
David Brown wrote
Rod Speed wrote
David Brown wrote
Rod Speed wrote
David Brown wrote
Rod Speed wrote
David Brown wrote


Having no experience with windows software raid, I did not know if
there were any complications involved (such as raid setup
information stored in the system registry).

That can obviously be backed up even if it is the case.


Registry backup is easy - restoring specific parts of the registry is not necessarily easy.

I did not know if there were likely to be risks involved, such as
it being too easy to delete your good mirror by making it part of a
new raid, instead of rebuilding the raid. That's why I asked.

You initially proclaimed that there is no point in mirroring with
Win.

That was just plain wrong.

But I am now happy to hear that recovery from failure in this
situation is straightforward, and therefore this sort of raid setup
does offer useful protection.

If you are are not interesting in recovering when something
has gone wrong,

Obviously the OP is.

you might as well backup to write-only media.

Having fun thrashing that straw man ?

There are a *lot* of people who effectively backup to
write-only media

There arent really that many anymore. Essentially because write
only media is so slow and of such limited capacity.

Perhaps you missed the point.

Nope.

"Write-only media" is media which cannot be read back, such as
writing to unformatted tapes,

Which like I said, doesnt get used much anymore for home system
backup.

or using encrypted backups without keeping track of the key.

Thats not write only media, thats a fucked up backup.


You've *almost* got the point. "Write-only media" is media that cannot be read at all - it's not something that *anyone* would knowingly use at any time. But people *do* use it by mistake, thinking they are doing a proper backup.


To quote from Wikipedia:

Write-only memory is the antithesis of read-only memory (ROM). By definition, a WOM is a memory device which can be written but never read. Since there seems to be no obvious utility for such a memory circuit, from which data cannot be retrieved, the concept is most often used as a joke or a metaphor for a failed memory device.


Maybe you thought I was talking about WORM drives or something like that?

That's why testing your restore procedure is so vital - many people
believe they have good backup procedures, but have problems when
they have to do a restore.

Thats much less common now than it used to be.

<http://www.linuxjournal.com/article/6435> <http://en.wikipedia.org/wiki/Write_Only_Memory>

None of that is any news to anyone with a clue.

- I'm sure you've met plenty who think they have a good backup system until the day comes when they need to do a restore.

Sure, but thats rather less common now.

But fair enough, it's a straw man here.

It is indeed.

Remember, I had originally made a suggestion of just using 500
GB of the 750 GB for raid for storing data (see the details
earlier in this post). I know it's straightforward to access
this data on a Linux system even if drive with the OS has
failed - you can boot a live CD, and mount it directly.

You can with Win too.

How do you recommend doing a live Windows CD boot?

Barts is very convenient.

Its easier to use a Linux live CD for a Win system tho, basically
because it doesnt have to be built, just burnt.

I've seen some suggestions on the web, but they were mostly hacks
of some sort.

Barts isnt.

If you know of a good way to make a general bootable windows CD
with recovery tools, I'd be very interested.

Barts.


Thanks - that is useful information. I'll have a good look at it this evening.

I find Linux live CDs useful for recovering problematic windows
installations, but I'd be happy to expand my toolkit.

Barts is a lot more configurable and you can for example build a bootable CD that includes various tools that you might need when still working out what the hardware problem is if it isnt just a
simple hard drive failure etc or you prefer to continue to use the
Win UI when recovering instead of having to understand the basics of Linux enough to be able to use that for the recovery.


I am happy using a Linux live CD for a lot of hardware issues, and for some software recovery issues (like copying data out of the machine, reseting administrator passwords, running a ClamAV scan). But most tools for finding and removing malware are designed to run natively on windows - being able to run these from a live CD will be a very useful tool.

There are others like the Ultimate Boot CD for Win that isnt strictly
speaking legal in the sense that some licensed software is included.
Corse you can always buy the licenses for whats included if you
want.


I've just had a quick look at their website. It's possible that it would be useful for some things, but I think that combination of System Restore CD (useful for low level stuff, such as disk imaging), Knoppix (nice for higher level stuff like finding files and copying them over to other systems), and now Barts (especially for malware scanning) will cover what I need.

So for Linux, it's a perfectly reasonable setup with a
different balance between efficient use of disk space and
redundancy and uptime than you would get with a full drive
raid.

But I'd like to be absolutely clear on this one - is it equally
simple with Windows software raid,

Yes. And you can use a Linux live CD to do that too with Win.

If Linux live CDs can access windows software raid, then that's a
good familiar safety net.

The main downside with that approach is that you do need to
understand the basics of Linux or choose a Linux thats very close to
Win UI wise etc.


True enough. In this case, it's for my own use, and I'm happy with Linux and/or Windows. However, there are always some things that are easier or more familiar in one system rather than another, so it will be useful to have a Barts CD lying around.

Even with a Linux thats very close to the Win UI, its not quite as
convenient to use the rather different UI with smartctl instead of
say Everest which is rather more convenient to use with a Win live CD
to get a look at the state of the hard drives when deciding what has
died etc.


Agreed - having the second disk external is much better (I think I
mentioned that myself in an earlier post). It also means it can be
disconnected when you are not running backups (reducing wear on the
disk, and risks of any user / OS / malware issues), and you can
easily connected it to another machine.

Copying to CD or DVD is still very popular - it's a familiar
solution for many people.

And is very viable for backing up only the irreplaceable data and
being prepared to wear the extra effort of a full reinstall in the
very unlikely event of say a hard drive failure or fire etc.

And perhaps the use of internet-based backup is more common here in
Norway than in many other parts of the world, since we have a high
percentage of users with fast (10 Mbit) broadband connections.

It isnt all that commonly used because much of the world uses DSL
that doesnt have that fast an upstream speed.

Very viable for incremental backup but not really that viable for
full backups for most.


Here in Norway, fibre based systems (or cable in cities) is increasingly common. I think something like 60-70% of the households in my town (about 3500 people, I believe) have fibre for TV, telephone and Internet access - with the minimum Internet speed being 10 Mbps up and down. You can copy a DVD's worth of data in about an hour and a half at that speed, which is a lot of photos.

Either way, I don't think desktop raid is a big gain for data
security.

Only in the sense that hard drive failure is uncommon.

Yes, hard drive failure is uncommon - especially in comparison to
other causes of data loss such as user error.

Depends on the user.

I personally have a completely different backup scheme for code with
a high backup frequency manually initiated where I do another copy of
the current code at every major step in the process of writing and
modifying the code, to the same hard drive the code lives on, with
the code also included in the normal backup scheme as well.

That allows you to handle gracefully the all to common situation where you decide a particular approach to the code will be useful but
it turns out to have a major downside that you didnt realise, so you
can step back to where you were before that sidetrack etc.


You need something like that for coding - some sort of source code management is invaluable. I use subversion on a server, but the best solution depends on the kind of coding you do, how you like to work, etc.


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