Should my backup device use RAID 5 or RAID 1?

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MountainX

Limp Gawd
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Mar 2, 2008
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I'm building a box, to be used for holding backups, with two older 3ware raid cards and 8 drives. It will be used for backups only. My main file server uses an Areca raid card set up as raid 5.

The backup box has smaller hard drives. I am setting it up as raid 0 so it has enough space. My logic is that since it only holds backups of data that already exists on the raid 5 array of my main file server, it should not be a disaster if a HDD crashes. I'll simply fix it and make a new backup.

I would have preferred to use JBOD, but I didn't have that option. Plus, given that it is an older computer, I thought the speed of raid 0 would be nice.

Any problems with this setup? Would people here strongly recommend raid 5 on the backup box too? Even if the backup box would then not have enough space to hold a complete backup? (I would have to selectively backup only the more important data.)

Thanks.
 
Raid 0 is fine for backups, if you don't mind the potential for data loss while it's down. A power glitch in your house, for example, could more easily kill enough drives to lose your data with raid 0 than raid 5. I tend to run raid 1 most places, but that's because my data requirements are pretty small. When I need more space than raid 1 gives me, first I consider what buying enough drives to do raid 1 would be, and if that's too much I run raid 0 or 5, depending on how much I need this data.
 
Thank you - that is a helpful perspective. Given that I have a really good UPS and generator system, I think I'll try RAID 0. (And I'll probably copy the really important data onto DVDs too.) My computers didn't even go down during the big storms the last few years, so power spikes or glitches should be pretty rare.
 
No no no!

RAID0 is striping, RAID1 is mirroring. If you use RAID0 and lose your array, all your data is gone because there is ZERO redundancy with RAID0.

I prefer to used RAID5 over RAID1, because of more fault tolerance.
 
RAID5!!! I _CANNOT_ STRESS THIS ENOUGH!

You only lose one drive's worth of space and you gain redundancy. with a RAID 0 array as mentioned above you lose EVERYTHING if a _SINGLE_ drive goes down! you have your disk arrangements set up wrong, if anything your main system / data server and your backup should be setup with 0 on the main for speed and 5 on the backup for data security, not with 0 on the backup! RAID 0 isn't really RAID at all, since it's not redundant.

Optimally, RAID 5 on both for extra redundancy and make sure that no 2 drives are from the same batch.

--neg
 
Yes as for someone who is new to RAID (not pc building) I must give a vote for RAID 5 also. I just got it set up and running this morning and all is well. Will continue to add drives as time passes.
 
Vix said:
No no no!

RAID0 is striping, RAID1 is mirroring. If you use RAID0 and lose your array, all your data is gone because there is ZERO redundancy with RAID0.
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The way I read it he was using a seperate machine where this raid is so it's a mirror backup so if one drive does fail and kills one array he will still have a second in order.

To that end I think raid 0 is an acceptable solution if you want something easy and aren't phased that if both systems (backup and original) lose drives before yo have time to rebuild and re-image you will loose the data for good. I'd say if you react within a day the chace of two systems losing the raid is pretty low unless you have some really unfortunate luck.

But yeah, I do agree raid 0 isnt THE safest option, but I do think it's work assuming it's only keeping a 100% backup.

edit: furthermore his main server is already in Raid5 too.

My only query would be whether the backups are ones you may want to roll back to occasionally or are just an emergency measure...if so definetly stay away from raid 0
 
Smigit said:
The way I read it he was using a seperate machine where this raid is so it's a mirror backup so if one drive does fail and kills one array he will still have a second in order.

To that end I think raid 0 is an acceptable solution if you want something easy and aren't phased that if both systems (backup and original) lose drives before yo have time to rebuild and re-image you will loose the data for good. I'd say if you react within a day the chace of two systems losing the raid is pretty low unless you have some really unfortunate luck.

But yeah, I do agree raid 0 isnt THE safest option, but I do think it's work assuming it's only keeping a 100% backup.

edit: furthermore his main server is already in Raid5 too.

My only query would be whether the backups are ones you may want to roll back to occasionally or are just an emergency measure...if so definetly stay away from raid 0
Click to expand...

You were reading correctly. I have a main file server that uses raid 5. This machine is for backing up that data only. If it dies, I have only lost a backup copy. I have not lost my original data. I'll simply make another backup copy when I restore the backup machine.

I went with raid 0 already and I think it was the right choice. I would have used JBOD if that had been a choice on my controller cards, but it wasn't.
 
Vix said:
I prefer to used RAID5 over RAID1, because of more fault tolerance.
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It is my understanding that RAID 1 or RAID 10 have more fault tolerance than RAID 5. With RAID 5 you can only lose 1 HDD. With RAID 10 you could lose multiple disks without problems under many scenarios. (There are also scenarios where losing two disks would be a problem, but the fault tolerance is greater than RAID 5 nonetheless.)
 
Smigit said:
My only query would be whether the backups are ones you may want to roll back to occasionally or are just an emergency measure...if so definetly stay away from raid 0
Click to expand...

Just regular emergency backups. I don't have any plans for roll backs. I'm not even sure what that means exactly.
 
MountainX said:
Just regular emergency backups. I don't have any plans for roll backs. I'm not even sure what that means exactly.
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By rolling back I just mean restoring the server to a previous point in time. But yeah, if the server has raid5 already then I don't think it matters a huge deal what raid you have on the other backup drive. You already have redundancy in the raid 5 so a raid0 will be a sort of last resort. I think you'll be fine.
 
Raid 1 or 5 is about the same for a desktop system, they both provide fault tolerance and if 1 drive fails it easy to replace and continue like nothing happen. However in both cases if more then 1 drive fail you lose it all.

RAID1 is a very simple way to have some real time data backup. It's most often the best to use on a desktop system as it cost the least to implement. Requires less space, power and the easiest to setup and maintain.

RAID 5 has made it to the desktop. There is some advantages to RAID 5 but is more expensive it uses at least 3 hard drives and is a little more complicated to setup.

Also know that RAID does not protect you from data corruption or Viruses. This is a real time back up.
 
MountainX said:
It is my understanding that RAID 1 or RAID 10 have more fault tolerance than RAID 5. With RAID 5 you can only lose 1 HDD. With RAID 10 you could lose multiple disks without problems under many scenarios. (There are also scenarios where losing two disks would be a problem, but the fault tolerance is greater than RAID 5 nonetheless.)
Click to expand...

Losing 2 disks could cause a total failure on RAID 10 if they are the 2 disks that have the same data as each other in a 4 drive array. Same as losing 1 in a RAID 0 array. Broken stripe. On the other hand, if you lose 2 disks at once, you probably have bigger problems. Still, a 4 drive RAID 10 is faster than a 3 disk RAID 5, and if I had the money and space for 4 drives, I would go RAID 10.
 
Well if you are doing backup to begin with, must mean you don't want to loose the information. Best thing for backup is removable drives. That way you can back up your information then put the drives into a fire proof safe or take them off site. I have been a volunteer firefighter for 3 yrs now and I have seen buisness loose all their information because of a fire. Backups do you no good if they are not safe from everything.
 
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