Breaking raid 1 mirror for offsite backup

[babybob]

Hi

We are considering a NetGear ReadyNas Duo for backing up images of our servers onto daily. We are also looking at offsite backups and wondered what peoples opinion / experience is of pulling one of the caddies out and putting a spare in, then taking the one we remove offsite? Other than the damage during transport issue are there any other things that might cause a problem?

Also if we go ahead with this, who actually sells spare caddies in the uk, struggling to find anyone

[mdgm]

No. Backup to a USB disk. Have a read of the backup link in my sig

[babybob]

Hi

Thanks for the link, Ive read through this but just wanted to go over a few of the articles points:

Second, when you pull a disk, there are multiple levels of commit that you have just broken. What guarantee do you have that the NAS wasn’t right in the middle of saving a file right when you pulled the disk? Just because you made sure all your clients were not writing anything doesn’t mean the NAS wasn’t clearing a cache or something – you simply do not know. When you do not know, you should EXPECT corruption.
Third, your file system is not cleanly dismounted. Think about it. Say for instance you want to keep a safe copy of your Windows data somewhere, and you are planning to pull the disk that is in your Windows machine. Wouldn’t you make sure you did a clean shutdown and the drive is dismounted properly before pulling out the disk? You wouldn’t just pull the power plug and kill the machine, then pull the disk right? That’s exactly what you are doing to the contents of the disk when you hot-pull a RAID1 drive.

We would always intend to shut down the NAS to pull a disk out so Im guessing this is a none issue?

Fourth, think of what RAID1 is all about – protection against drive failure. Now, think about how hard your drives are working during a typical day. Failure is most likely when the drive is most busy. If each day you hot-pull that disk, not only have you just walked away from redundancy until your new replacement disk is all mirrored again, you’ve also just put your drives to work – HEAVY work – remirroring. Guaranteed your disks are working waaaay harder during the re-mirror process than at any other time during the day. So just when they are most likely to fail (when they are working the hardest) you have also intentionally removed the RAID protection at this same time too – that’s just plain CRAZY!

Surely there is no difference in disk usage between mirroring from one raid disk to a new one, and copying a single large (an hard disk image in our case) from the nas to a usb drive every day? I do however see you point about having a degraded raid array whilst it mirrors to the spare disk you insert (we were inteding to have 3 disks in today, swapping 2 out every other day), but bearing in mind this is the backup, not the actual files (which are on a raid server themselves) thats not really a huge risk?

Just not sure I really see why a usb harddrive will be any better than cold swapping a disk from a mirrored raid array?

[WhoCares?]

Just not sure I really see why a usb harddrive will be any better than cold swapping a disk from a mirrored raid array?

Maybe because while/after saving to the USB Drive you still have a redundant array protecting your data. But since data protection is not what you want, you may as well do as you intend to.

-Stefan

[babybob]

Hi Stephen

Thanks for helping me think through the pros/cons will think some more but appreciate your experience

[WhoCares?]

I'd advise you though that once you're going down that road you should at least do a test run and see whether you can actually get your data back from one of the "removed and stored elsewhere" drives. Could be more difficult than it may seem and if it's too much of a hassle would render your approach nearly useless anyway.

-Stefan

[TeknoJnky]

ultra 2 + ultra 2 + readynas replicate.

[Grievous]

babybob, I dug through some old posts of mine and found a couple that are relevant to your plan, and explain why it's a bad idea.

viewtopic.php?f=25&t=27855&p=154032&#p154032
viewtopic.php?f=65&t=26952&p=148849&#p148849

[WhoCares?]

As far as I understood his posts he's quite resistant to reasoning that's why I suggested the "live trial".

-Stefan

[Grievous]

Or he's simply still looking for information, which is why I posted links to two of my older posts on this exact subject, providing more information. The two things that seem to have been skipped are the SATA connectors, and ESD on the drive being moved away as a "backup"

[WhoCares?]

As a sidenote: I think it would be easier to convince people that backups to an external drive are the way to go if there were an eSATA connector on the boxes. USB 3.0 on the newer 2bay boxes helps but USB 3.0 external drives are still rare - at least over here.

-Stefan

[Grievous]

USB 3.0 drives aren't particularly common here either, but the chassis are still cheap(around 30 bucks) and available so you can simply build your own.

Besides, you'd be better off rotating between two external drives anyway, rotate once a week and you've got a week(most will have no trouble completing overnight 1 night a week) for your massive backup job to complete.

[babybob]

thanks for all your feedback guys, I will do as suggest and test how easy it is to actual get data off the pulled drive. Thanks for the other links, the sata connectors wearing out seems another valid reason so definitely one to consider.

[Grievous]

thanks for all your feedback guys, I will do as suggest and test how easy it is to actual get data off the pulled drive. Thanks for the other links, the sata connectors wearing out seems another valid reason so definitely one to consider.

You seem to have missed the part about ESD killing the bare drive you're handling which you assume has a safe copy of the data as you're putting it in it's secure/safe location for storage. This is why external drives are typically in a chassis instead of just handled bare(which you can do with some docking stations, but there's still an ESD risk).

BTW, ESD = Electro Static Discharge. More commonly simply referred to as the shock you get touching a door knob, but it doesn't necessarily require as much as it takes to feel, as it does to cause problems.