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RAID Info & Rundown

nhuisman1234

nhuisman1234

macrumors newbie
Original poster
Dec 7, 2008
9
0
Hey,
I own a Mac Pro (http://support.apple.com/kb/SP30) with 6GB RAM, 750GB SATA and 250GB SATA. I want a good backup option, I am thinking that RAID might be the best option. I know a lil bit about the topic, not a lot. Just that there are different kinds, 1.0.5.etc. and that they all do different sort of backup. Heres my questions I guess: Can someone simplify some more info on RAID? Should I buy a couple 1TB drives and use them instead of an external NAS? Can I do this w/o the internal RAID card? AM I ASKING DUMB QUESTIONS?
Thanks for your help.
 
RAID is not a backup system! It is used for speed, high availability, or both. But not backup.

Do a Google search on RAID or search here on RAID.

Most people would be better off using Time Machine along with regular image backups using SuperDuper! than using some form of RAID.

S-
 
RAID is not a backup option. It allows you to start again quickly in case of a drive failure that's it. Or to have a faster system.

It doesn't protect against theft, fire or your own mistakes.
 
But you can use RAID as a device to store the backup. Many external devices like enclosure and NAS do support more hard disks and can be used to build a RAID.

You first need to decide if you want to back up to a NAS, an external drive or else. Then you can decide to use a RAID in one of those devices. That will ensure the redundancy of the backed up data (for example if one of the two HDs of a RAID 1 dies you will still be able to access the data on the remaining drive).
 
The two most basic modes of RAID are 0 and 1.

RAID0: Is used to speed up writing and reading on disk drives. Instead of I/O to one disk the system uses two drives and splits the data stream into little portions. While drive1 is absorbing those data it already feeds drive2 with more. The size of the data portions is called a stripe size. RAID0 is also referred to as striping

RAID1: Is used to have a redundancy. Instead of writing to one disk the system writes everything twice. This is why it is also called mirroring. A mirror RAID1 is used when the user cannot afford to wait for loading a backup and needs the system to run in case of a single disk failure. Redundant disks do not replace backups as already said.

Your Mac Pro allows for both version of RAID without the installation of hardware. You can use up to six internal SATA ports to run RAID arrays with the OS X SW RAID facility. You find it in disk utility.
 
nhuisman1234 said:
Hey,
I own a Mac Pro (http://support.apple.com/kb/SP30) with 6GB RAM, 750GB SATA and 250GB SATA. I want a good backup option, I am thinking that RAID might be the best option. I know a lil bit about the topic, not a lot. Just that there are different kinds, 1.0.5.etc. and that they all do different sort of backup. Heres my questions I guess: Can someone simplify some more info on RAID? Should I buy a couple 1TB drives and use them instead of an external NAS? Can I do this w/o the internal RAID card? AM I ASKING DUMB QUESTIONS?
Thanks for your help.
Click to expand...
Wiki's RAID page will help get you started on the differences in the levels.

But please pay attention to both sidewinder's and Angelo95210's posts. The use of RAID as a backup isn't recommended unless it's a true backup (NOT also used to maintain the primary data - that needs to be on a separate drive/s or array itself).

And before you ask, even a RAID 1 isn't a backup. That's where the "It can't help you from your own mistakes" part comes in. If you screw up and delete a file/s you needed, it will be repeated on the RAID 1. :eek:
 
With your intended purchases you would have 4 GB of disk space on four drives (1,5; 1,5 ; 0,75; 0,25). It is your intention to have good backup and do this internally as long as possible. Your drives would not give you such a good shot there. You need roughly the same capacity for backup that you would need for storage. So if you can afford more large drives it would be better.

For starters you could RAID0 the two 1,5 GB drives and put everything on it. Then you would concatenate the two other drives (JBOD) and use them for backup until you come to the capacity limit of 1 TB. At that time you should be prepared to buy two more 1,5 TB drives.

If you want it simpler run everything from one of the 1,5 TB drives and use the other one for backup. Make an estimate how fast you data will be growing to determine your approach.

RAID1 doesn't make much sense in your situation.
 
gugucom said:
For starters you could RAID0 the two 1,5 GB drives and put everything on it. Then you would concatenate the two other drives (JBOD) and use them for backup until you come to the capacity limit of 1 TB.
.
.
.

RAID1 doesn't make much sense in your situation.
Click to expand...

Wow. Use a JBOD array to backup a RAID 0 array. Let's just poor gasoline on a fire! He said he wanted a good backup option....

S-
 
nhuisman1234 said:
Hey,
I own a Mac Pro (http://support.apple.com/kb/SP30) with 6GB RAM, 750GB SATA and 250GB SATA. I want a good backup option, I am thinking that RAID might be the best option. I know a lil bit about the topic, not a lot. Just that there are different kinds, 1.0.5.etc. and that they all do different sort of backup. Heres my questions I guess: Can someone simplify some more info on RAID? Should I buy a couple 1TB drives and use them instead of an external NAS? Can I do this w/o the internal RAID card? AM I ASKING DUMB QUESTIONS?
Thanks for your help.
Click to expand...

Excuse me... Don't worry, your not the only one. There are loads and loads and loads of users on this very forum who seems to think RAID arrays/solutions/installations would make a good archiving system.

Curious, why are you/others/everyone under the impression that a RAID would be a good backup solution? Why???

Firstly, RAID isn't a backup solution period. Putting aside it's initial setup costs; it'll still have the potential of failing like any other hard drive based storage system, the only benifit a user gets from RAID is extra large volume storage, typically, multiple terabytes with workstation/server data transfer rates.

.. also, you have to remember, the higher the number of mechanical hard drives in your array, the higher the risks you'll run for something to fail. Worst, if those drives in uses are purchased from the same batch, there's a even higher risk for everything grinding to a halt!!

If you want a mass backup solution, for data and media archiving the only way to go is Blu-Ray, 25Gb (single layer), 50Gb (double layer) on a single disc and if you have the budget for them, there's 100gb discs from TDK and Sanyo but really really expensive!!). For long term storage, there's long life archiving media, they are good for 50 years storage. And if your data is critical, make multiple copies and store them in remote locations - in case of burglary/fire/earthquake etc.
 
UltraNEO* said:
If you want a mass backup solution, for data and media archiving the only way to go is Blu-Ray and if your data is critical, make multiple copies and store them in remote locations - in case of burglary/fire/earthquake etc.
Click to expand...

The risk of the backup drive(s) failing and the primary drive(s) failing is usually very very high. We use disk backup at work for everything, and it works flawlessly and we've never lost a bit of data. You're painting a clear picture of FUD.
 
belvdr said:
The risk of the backup drive(s) failing and the primary drive(s) failing is usually very very high. We use disk backup at work for everything, and it works flawlessly and we've never lost a bit of data. You're painting a clear picture of FUD.
Click to expand...

Hey... didn't say you can't run the risk... if your happy, then keep to your existing methods. Though most companies don't have a single array like a typical home user would. Companies usually have something like a SAN on the network... for most people they're out of budget.
 
UltraNEO* said:
Hey... didn't say you can't run the risk... if your happy, then keep to your existing methods. Though most companies don't have a single array like a typical home user would. Companies usually have something like a SAN on the network... for most people they're out of budget.
Click to expand...

Not entirely. Most companies have a SAN in production, and may have a SAN for backup. In some configs I have seen, there are servers, each with their own dedicated DAS array. But for the most part, the backup disk devices are usually not high speed storage, but can be devised in a SAN-like architecture.
 
sidewinder said:
Wow. Use a JBOD array to backup a RAID 0 array. Let's just poor gasoline on a fire! He said he wanted a good backup option....

S-
Click to expand...

Well, this is obviously not going to be a production system or he would have specified that.

I also told him his simplest option is using the 1,5 TB drive and backing up on the other 1,5 TB. Forget the other drives or use them to store a clone of the initial installation. Or for Windows, whatever needs he finds.
 
RAID just seems like the smart choice because of the idea of having your data split over 2 HD's that can rebuild if 1 fails. I want to keep my HD's to a minimum. So I may just get 2 1.5TBs and use the sell the others or run XP on bootcamp. But I am also seriously considering a good NAS setup to. Another question. Is DROBO worth that kind of coin for what you get? I wanna keep all my backup costs to under 500US. What is the best setup I can get for that, on-location, hard-drive based, setup that is.Thanks
 
You seem to oscillate between penny pinching and big spending. If you are so keen to do RAID1 redundancy why don't you buy three of those 1,5 TB disks. Two you run in disk utility RAID1 and the third you use for internal backup. That would be much cheaper than an external solution, particularly an expensive one like the drobo.
 
gugucom said:
You seem to oscillate between penny pinching and big spending. If you are so keen to do RAID1 redundancy why don't you buy three of those 1,5 TB disks. Two you run in disk utility RAID1 and the third you use for internal backup. That would be much cheaper than an external solution, particularly an expensive one like the drobo.
Click to expand...

Hmm, I think what I'll do is buy 4 x 1.5TB and RAID 1 them. One half for business the other for personal. What are the odds of drive failure if they're all in the unit? Im not concerned about offsite backup or external. Make sense?
 
nhuisman1234 said:
Hmm, I think what I'll do is buy 4 x 1.5TB and RAID 1 them. One half for business the other for personal. What are the odds of drive failure if they're all in the unit? Im not concerned about offsite backup or external. Make sense?
Click to expand...
RAID, no matter the level, is NOT a backup system. Primary data and backup data must be disconnected from one another, so it can't reside on the same drives or array. In the case of a mirror, though it's 2 drives, it's still the same array.

So if you screw up, it occurs on the duplicate drive as well (no stopping it, as it's automatic). Period. An accidental deletion is a perfect example, and the result is the data's gone. Bye-bye, kaput,...

There's issues with the other array types as well. The simple answer is, backups must be on an independently operated separate drive, or array from the primary data.

If you wanted to make 2 RAID 1 sets, use the first set for the primary data, and the second set as a backup location, that would work. But it's also foolish in this case. If you needed 24/7 system availability (uptime), RAID 1 is fine for the OS, apps, and data. But you'd only need a single drive for backup (just make sure it's capacity is large enough).
 
nhuisman1234 said:
Hmm, I think what I'll do is buy 4 x 1.5TB and RAID 1 them. One half for business the other for personal. What are the odds of drive failure if they're all in the unit? Im not concerned about offsite backup or external. Make sense?
Click to expand...


I don't see the need for different drives for privat and business data but you may have reasons. It seems to make some sense to run that way but it will commit you to external backup. External backup needs a SATA or RAID card to be effective and fast and you are looking at a big increase in cost for that.

You also can get bigger internal drives of 2 TB which are better than the 1,5TB if you have cash to burn. Perhaps you want to partition those drives for a privat and a business partition of 1 TB each. You can then still have separate partitions, redundant drives and internal backup. You would need three drives for that as nanofrog pointed out. The fourth can be a 750 GB Windows drive.
 
gugucom said:
I don't see the need for different drives for privat and business data but you may have reasons. It seems to make some sense to run that way but it will commit you to external backup. External backup needs a SATA or RAID card to be effective and fast and you are looking at a big increase in cost for that.

You also can get bigger internal drives of 2 TB which are better than the 1,5TB if you have cash to burn. Perhaps you want to partition those drives for a privat and a business partition of 1 TB each. You can then still have separate partitions, redundant drives and internal backup. You would need three drives for that as nanofrog pointed out. The fourth can be a 750 GB Windows drive.
Click to expand...
There's not much to go on, and it makes me doubt the need for a mirror at all. If it's not needed, it's a waste of money and drive locations. HDD bays in the MP's are precious, as it doesn't take long to fill them. ;)
 
Okay. So I just purchased a 750GB Seagate. This is how Im gunna set up my Mac Pro.
Have my 250GB house all my applications are settings.
Have my first 750GB store all my Business files.
Have my second 750GB store all my personal files.

Now I need to move on to a backup solution. Im really persuaded to go to a 2 drive NAS setup. Then purchase 2 x 1.5TB HD's and RAID 1 them. And backup both 750 drives. And use Carbon Copy Cloner to clone both 750's.

Is this a easy/smart way to use what I have to guarantee a seamless copy?
Any issues with CCC and a RAID 1 drive?
Should I partition my RAID 1 into 2 drives, or does it see the 2 automatically?
Thanks in Advance
 
don,t forget the bathtub curve or MTBF


one drive say 10,000 hrs MTBF
two drives in a raid 10,000 MTBF each give a bathtub curve of 5,000 hrs MTBF

so if you use a raid as a backup spinning reserve thing very closely as to the quality of the drives them selves server grade are the minimum ,enterprise drives would be better


the only safe backup is a removable storage that is arranged with farther ,grandfather and great grandfather drives store of site


Its a long time ago now when I was at work, when 1 tb took up half of the computer room floor space at a data centre , but we had the tape backup robot storage located in an under ground vault behind two vault doors , the banks took there backup very seriously in those days
 
Lordedmond said:
one drive say 10,000 hrs MTBF
two drives in a raid 10,000 MTBF each give a bathtub curve of 5,000 hrs MTBF

so if you use a raid as a backup spinning reserve thing very closely as to the quality of the drives them selves server grade are the minimum ,enterprise drives would be better
Click to expand...

Why does a Raid reduce the MTBF?

I have a 8 disk Raid of 500GB WD RE3 running 24/7 for about 2 years now. Should I consider swapping the disks with new ones?
I really want to keep that system as long as possible, as it is one of my backup devices.
 
its because you have ( in a two disk case ) twice the number of parts therefore you have double the chance of failure , its not quite as bad as that but you will have a greater chance of failure with the increased number of drives
 
Ok, that makes sense!
So the MTBF remains constant for the single drive, but is reduced for the complete array.
To be honest, I never thought about that. :eek:
 
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