Supid quesion? Can you use a RAID as a backup device?

[chockomonkey]

Is it possible to set up a RAID 1 with hot-swappable drives as a means of a backup utility?

Say that i had 3 drives and 2 were set up on a raid. could i swap out one of the drives weekly/monthly and have it continue to mirror the first drive? (ie fill in the blanks that were left from not being plugged in for a week/month and make changes that had occured)

or is this just silly?

Thanks,

-Chocko

[The_Engineer]

there is no reason to swap them out intermittently -- just keep one handy in case a drive fails as the data is already backed up constantly to its paired drive in the system. The caveats to this are as follows:

1. Make sure to fully test your standby drive before just letting it sit. Drives often are bad from the manufacturer or go bad very quickly (within the first few hours of usage) once the drive is confirmed good it can sit for a long time and will be a good safety precaution for you in case one of the two drives fails.

2. Asses how critical your data is. Depending on how critical it is that you have a backup you may want to set up some sort of an off line backup, in a separate geographic location for the most critical data, but not necessarily the entire drive.

Scenario: You bought 3 OEM drives from newegg, they have sequential serial numbers or close to it meaning it is likely they were manufactured in the same batch. It is now 3 years from the date of purchase and 2 of the drives have been operating reliably in the raid the third sitting at standby the entire time -- it is possible that the 2 hard drives will fail in a time frame that is close to one another given their similar lifespans. Again it is for this reason that you must asses your needs of how critical this data is to you.

Possible solution to prevent data loss in the scenario above:
Have a total of 6 drives
2 in the array
1 standby
3 sequential backup USB drives that are stored off-site and only brought on site to back up the partition existing on the array at predetermined intervals, say 3 times a year, or 3 times a week, depending again on the criticality of your data.

I really think that a backup USB drive or off site backups burnt to DVD etc are going to be a better way to preserve your critical data than rebuilding the array every so often especially as this is a process that causes unnecessary wear and tear n the drives and really provides no substantial benefit when compared to a backup created by a good backup utility.

If you would rather listen to a bit of wisdom from someone who knows much more than I on this topic Try this page (http://macbreaktech.com/4/zulu-foxtrot-sierra-zfs/)

Sorry if the answer was long winded but I hope it helps you decide your needs.

[chockomonkey]

Engineer, thanks for the response!


How much extra wear and tear is excertet on drives when they have to "fill in the blanks" in order to become a mirror again? It seems to me that it should be exactly the same amount of wear as the initial write of the data... am i mistaken?

As it is now, i am using two usb drives which i change each week and run a backup. The spare is kept in the same room as the server, but in a fireproof safe. (this thing is huge, came with the building as it is so big, the room it is in was built around it.)

This method (at least to me i guess) seemed a bit clunky as far as my time spent trying to minipulate the software and get the drives to work how i want. Which is why with the prospect of building a new server i was looking for something easier (hence this idea, where i could just unplug one, and plug the other in and have it do its thing.)

Perhaps i just need some new software? I'm using Retrospect... i think it came with the two external WD harddrives that i bought for this...

Thanks again for the help!

[Ockie]

Is it possible to set up a RAID 1 with hot-swappable drives as a means of a backup utility?

Say that i had 3 drives and 2 were set up on a raid. could i swap out one of the drives weekly/monthly and have it continue to mirror the first drive? (ie fill in the blanks that were left from not being plugged in for a week/month and make changes that had occured)

or is this just silly?

Thanks,

-Chocko

You can do that and I have seen those who have. Just remember, pulling drives out of a perfectly good array can cause problems, you can get corruption, data loss, etc. If you want to do this, make sure you got a good pair of drives, good hot swap unit, and a great controller.

In other words, don't bother :) Just keep the drive on RAID and when it dies, swap it out. You can also use a offline backup solution by just backing up your array once in a while.

Engineer, thanks for the response!


How much extra wear and tear is excertet on drives when they have to "fill in the blanks" in order to become a mirror again? It seems to me that it should be exactly the same amount of wear as the initial write of the data... am i mistaken?

As it is now, i am using two usb drives which i change each week and run a backup. The spare is kept in the same room as the server, but in a fireproof safe. (this thing is huge, came with the building as it is so big, the room it is in was built around it.)

This method (at least to me i guess) seemed a bit clunky as far as my time spent trying to minipulate the software and get the drives to work how i want. Which is why with the prospect of building a new server i was looking for something easier (hence this idea, where i could just unplug one, and plug the other in and have it do its thing.)

Perhaps i just need some new software? I'm using Retrospect... i think it came with the two external WD harddrives that i bought for this...

Thanks again for the help!


The drives will struggle, but there is no real wear and tear on the drive other than just being loaded with data. I wouldn't worry about stress or excessive wear on a drive in this case.

How hot does that firesafe get in a fire? Keep in mind you can still have data loss if the safe can't withstand the heat, prolonged fire, or if the safe heats up the contents. Also, is the fire safe waterproof?


Why not run a RAID 1 unit with a hot spare. Then put in a nice hot swap for another large dump drive, do your backups on the dump drive and store the dump drive? It will be much faster than USB and much less tedious.

[chockomonkey]

Well that's two! Sounds like i may end up with more trouble than it is worth if i try to hot swap one of the drives in the RAID 1 array.

What you said Ockie though, gives me some hope!

Why not run a RAID 1 unit with a hot spare. Then put in a nice hot swap for another large dump drive, do your backups on the dump drive and store the dump drive? It will be much faster than USB and much less tedious.

By RAID 1 unit with hot spare, what exactly are you referring to?

It seems though i'll now likely have 3 drives in my server. 2 as a RAID 1 array, and then as you suggested another large dump drive to run my backups on. And then another 2 drives that aren't in the server at the same time as the other 3.

What software would you recommend for backups? As mentioned i'm using Retrospect (WD software i think, or at least it was free with the USB drives i got) and i don't really like it.

As for the safe, i'll have to look into that. I may end up choosing to run these dump drive backups on more like a month to month thing and keep them off site so should the building burn down, i just don't have to fret about it.

[Ockie]

By RAID 1 unit with hot spare, what exactly are you referring to?


A hot spare is an extra (unused drive) that sits in your array ready for activation in case another drive fails and takes over.

For example

You have 2 drives and one hot spare, known as A, B, C.

A
B
C

A and B are your active mirroring drives, C is just sitting there waiting to be used in an emergency.

Now lets just say B drive fails, C takes over and assumes drive B's position.

A
C

or

B
C


My explanations suck, but I think you get the idea. The logic behind this is to quickly have your hot spare take over so that the administrator doesn't have to rush to the scene, also it reduces the chances of a total data loss as the last remaining mirror drive may fail during the secondary downtime.



It seems though i'll now likely have 3 drives in my server. 2 as a RAID 1 array, and then as you suggested another large dump drive to run my backups on. And then another 2 drives that aren't in the server at the same time as the other 3.


Lets assume you use 150gb raptors

I'd run:

150GB Raptor (RAID 1)
150GB Raptor (RAID 1)
150GB Raptor (RAID 1 Hot Spare)
750GB HDD (Backup, good for a weeks worth of daily backups before needing to swaped out)



As for the safe, i'll have to look into that. I may end up choosing to run these dump drive backups on more like a month to month thing and keep them off site so should the building burn down, i just don't have to fret about it.

Usually its a good idea to keep one backup off site, even if it is at the admins house secured in a safe. (Not an ideal senario, but better than a single point of loss). You need to detirmine your companies time-to-float and then work your backup strategy from there, if your company can't go a day without information or they will tank, then perhaps it's a good idea to do more frequent off-site backups.

[Whatsisname]

as some people said, don't pull drives out of a perfectly good array. Leave them in there.

Also, no RAID will protect against accidentally overwriting something important or a mistyped "rm -rf", and so you should also take incremental backups.

And, like others mentioned, you should store copies somewhere else, in case of a flood or fire or something.

[chockomonkey]

Thanks all for your help, i've got a good idea of what i'm going to build and how i'll implement my backup.

I really appreciate the help!

[The_Engineer]

You can do that and I have seen those who have. Just remember, pulling drives out of a perfectly good array can cause problems, you can get corruption, data loss, etc.

I second this notion. Also the hot spare is a great idea. I'm sorry I do not have any info on specific software products as I am still in the process of setting up a backup server for home use here and have not yet gotten to the software portion of things. Best of luck!