So, raid 1... Is it actually reliable...

[NeilF]

So, if you get a two disc NAS unit with raid 1... How safe is that data.

It's many MANY years since I've had a hard drive go, so for me, the chances of two going at the same times seems very unlikely.

However, is part of the problem that infact the hardware that might take one drive down, might take both down?

 

[dustofnations]

Usually HDD failures are mechanical within the drive rather than an external entity destroying them, so the chances of both going simultaneously was pretty insignificant I should think.

There is a possibility though of course that both could go, hence corporate backups are often also off-site.

In the case of consumers like you and I, I'd think RAID1 provides adequate protection against HDD failure (unless you're unlucky).

Still always ideal to back up absolutely critical data off-site (some web-host), or onto some sort of ROM

 

[NeilF]

I seem to recall a thread a good few many years ago where there seemed to be an under current of feelings that a good number of people had suffered both their raid 1 disks failing at the same time...

 

[LeJosh]

The problem with RAID1 is that if the primary drive writes an error it writes that same error into the second drive... Mirroring isn't always positive. The chance of that is slim though I imagine but a huge pain!

 

[NeilF]

The problem with RAID1 is that if the primary drive writes an error it writes that same error into the second drive... Mirroring isn't always positive. The chance of that is slim though I imagine but a huge pain!

I guess - if the scenario fits - run the two disk autonomously, and just do a robocopy every couple of days...

 

[zsolmanz]

NeilFawcett, that's ok until you start writing tons to your HDD in those couple of days, at which point robocopy takes ages. You could do it over-night, but if your HDD is noisy and near your bed then that's not nice.

Not to mention that although that works well as a backup, it's then no different to a normal back-up system, whereas RAID 1 gives absolutely up-to-date protection against mechanical HDD failure.

Don't worry about there being multiple HDD failures at the same time. It doesn't happen very often, but if you're really fussed then invest in an Un-interrupted Power Supply and Surge Protection, which should stop anything but the worst of external effects from killing your PC. And if it's bad enough to screw one HDD, you'd be relying on your backups anyway.

The easiest way for RAID 1 to result in data loss is if one HDD goes down, and you're not quick enough to get hold of another. It is true that 2 HDDs doing exactly the same work will fail at similar times, because it represents the identical usage of the disks. What RAID 1 allows you to do is act on the warning of one failing (i.e. get a replacement for one or both) without losing any data. This is one of the reasons why it's best to buy identical HDDs for all forms of RAID.

 

[Audigex]

It can introduce an extra point of failure if the raid controller dies, but I generally trust silicon chips over mechanical drives. Software raid I have less faith in.

The simplest way to look at it, for me, is that it protects you from a single drive failing and allows you, more often than not, to continue using your data seamlessly.

At the same time, it can cause problems when people see it as a substitute for "regular" backups onto external media. If you don't have a second, seperate, copy of your data, you're vulnerable.

Basically, then, it's a handy extra to normal backups, allowing you to continue without having to swap drives around and protecting you from a common type of failure from one of the few mechanical parts left in a PC, but it can provide a false sense of security.

 

[aln]

RAID is not backup.

Restoring a large backup can be a pain, and take a long time. RAID is nice to mitigate having to go through that problem all too often, but if your data is important, back it up. Always assume the worse will happen someday (ie your house blows up), and have a recovery plan for that time.

On the other hand, I don't backup my data. I don't really consider the last few episodes of $program to be all that valuable.

 

[NeilF]

RAID is not backup.

Restoring a large backup can be a pain, and take a long time. RAID is nice to mitigate having to go through that problem all too often, but if your data is important, back it up. Always assume the worse will happen someday (ie your house blows up), and have a recovery plan for that time.

On the other hand, I don't backup my data. I don't really consider the last few episodes of $program to be all that valuable.

Absolutely... My 'dearest' data is backed up, and the backup is backed up in a different location. I can just imagine my house being burgled, or my study burning down, so both my PC and my lovely shiney USB backup drive next to it are both lost. So I have another backup elsewhere just incase.

I would be considering raid mainly for media... Which if I lost wouldn't be the end of the world... Just a big pain...

 

[AbsenceJam]

Hardware failure of the disk is the only thing RAID 1 protects against. If a cable goes awry, RAM is causing bad writes etc it doesn't help.