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Is RAID that much faster?

C

c073186

macrumors 6502a
Original poster
Nov 2, 2007
821
3
If I have one 500 GB hard drive, would I notice much speed improvement if I buy a second 500 GB drive and use Disk Utility to make it a RAID setup?
 
Depends on what you're using it for - do, however, bear in mind that RAID 0 (striping) means that only one hard drive has to fail for you to lose EVERYTHING as there's no built-in redundancy. Essentially, you've doubled your chances of losing your data.

A more sensible move would be to configure two drives as a RAID 1 (mirror), which doesn't improve speed, but does ensure an extra level of safety for your data - if one drive fails, your data is still safe on the second drive. The faulty unit can then be replaced and the array rebuilt without losing anything.
 
tersono said:
A more sensible move would be to configure two drives as a RAID 1 (mirror), which doesn't improve speed, but does ensure an extra level of safety for your data -
Click to expand...

RAID 1 DOES improve speed - READ speed is much better than a single drive, but not as good as RAID 0, however, WRITE speed is comparable to that of a single drive.
 
even software raid0 is a big improvement in speed. It's definately LESS reliable since if you have 3 drives you have 3x the failure possibilities, but its faster, and thats what backups are for :)

I just setup a 3x 500gb raid0 (software raid) in my mac pro, and a 2x750gb raid0 in an external eSata enclosure for time machine.. I was getting 8-9 gigabytes a minute transfer rates.. for the 2nd half of my backup that I timed, it took 19.5mins for 170.2gb of stuff to get backed up
 
So if I do RAID 0 with 2 x 500 GB drives and I backup to Time Capsule, I should be covered?

One other question: are the chances of having a hard drive failure very high? I mean if I have this setup and use it for several years, am I likely to run into problems at least once or a few times and have to reformat or buy a new drive?
 
if you have a backup of your data, then I would use raid0.. not sense doing a raid1 mirror if you already have it backed up elsewhere.

as far as reliability, it may work fine with no problems until you get a new machine, but hardware isn't always the most reliable thing.. you could have a drive up and die on you tomorrow for no reason, and its that reason that you have less reliability when you use raid0.. you have the data shared across drives, so it only takes 1 drive to lose it all

but like I said before, that's what backups are for
 
um....that post was basically incorrect.

raid 1 is slightly slower than no raid at all when writing, and basically the same as no raid at all when reading unless you're talking about concurrent reads, in which case, the number of RAID 1 drives you have can increase read speed on a 1-1 basis. For example, if you're copying a single 4 gb file (like a DVD) from one place to another, or duplicating it, RAID 1 will be the same speed as a single drive when reading. RAID 0 will be 30-70% faster depending on what's going on (in a 2 drive setup). But if you're copying 2 2GB files at the same time (say two different apps are doing the reading), then RAID 1 and RAID 0 will effectively be the same speed, and they will both be faster than no RAID at all, because RAID 1 can load-balance the read from multiple drives that contain the same data.

that's the only sort of situation where RAID 1 will be faster than a single drive.

to give you an idea what RAID 0 is capable of, a 20 drive external RAID 0 array connected to a hardware RAID controller can read/write over 600 MB/sec sustained by using multiple SATA channels. You can buy an appropriate controller card for the mac pro for 400-500 dollars on newegg, then build the array yourself for a couple thousand dollars and read/write multiple streams of uncompressed HD video.

Of course, you'd want to use RAID 5 or 50 or something more robust if you're doing 10-20 drives in an array and you have a hardware controller.

but the principle is the same...RAID 0 is most certainly, definitely faster than RAID 1 in almost every situation, and it is never slower. It is also always faster than a single drive by itself. How much faster depends greatly on the usage situation and the particular way that it is set up.
 
tersono said:
Depends on what you're using it for - do, however, bear in mind that RAID 0 (striping) means that only one hard drive has to fail for you to lose EVERYTHING as there's no built-in redundancy. Essentially, you've doubled your chances of losing your data.

A more sensible move would be to configure two drives as a RAID 1 (mirror), which doesn't improve speed, but does ensure an extra level of safety for your data - if one drive fails, your data is still safe on the second drive. The faulty unit can then be replaced and the array rebuilt without losing anything.
Click to expand...

Does Apple's DiskRepair formatting util. provide for building a RAID 1 or do you have to buy a third party util. like SoftRaid?
 
I am also very interested in read speeds of a RAID 1. Theoretically, reads could be almost twice as fast as from a single drive but it depends on how well Apple implemented software RAID1...

Are there any test results of a mirorred drive setup in the 8core MP? RAID0 seems to be a lot more popular than RAID1 but I tend towards redundancy
 
Disk Utility lets you use either.

I've had a great experience with RAID0 in a PC I own, I'd recommend it to anyone. Don't forget to Time Machine though :)
 
This is getting slightly off topic, but say I buy another drive and do a RAID 0 setup. Then some time down the road one of the drives dies. How would I fix that problem? Is it easy to diagnose which drive is faulty or is it a big hassle? I do not have a lot of expertise in this area so I don't want to do something that is going to cause a lot of headaches in the future.

And BTW; I am mostly using my Mac Pro for Office, web, mail, some iMovie/iDVD, iTunes, and iPhoto. So back to my original question: would I benefit much from going to RAID 0?
 
If disk utility reports an error, it should tell you which bay its in, or if you have a hardware failure / noise, you'd know, or you could just unplug one and power on and see which one it is.. either way, you'd have to recreate the raid set, and then restore your data
 
I think that for what you are doing you won't even need a raid. Just get some nice sized and speedy HDs and some ram.
 
In my experience, the performance advantages of the RAID configurations discussed in this thread are considerably more complex than some of the blanket statements would lead one to believe. Performance depends upon the number and geometry of the disk drives and the microcode of the disk controllers, not to mention the I/O scheduling algorithms of the kernel. Other factors are the degree of multi-tasking which will occur and how the data is distributed on the physical space.

Not a simple topic ...

Reliability, on the other hand, has been well covered in this and other threads. Unless you are getting into optimizing a server, I'd stick with simple and reliable.
 
benpatient said:
um....that post was basically incorrect.

You can buy an appropriate controller card for the mac pro for 400-500 dollars on newegg, then build the array yourself for a couple thousand dollars and read/write multiple streams of uncompressed HD video.
Click to expand...

Benpatient - could you please give me the part / model number that will REALLY work on the new 8-core Mac pro? I am into HD video editing and need to set up a good RAID system.
 
Given there are four bays in the Mac Pro, I endorse and have set up RAID 01:

-Four drives, two sets of striped drives combined to a mirrored drive.

Pros:
-don't need the hardware raid card
-really fast for disk writes...
-boot up and install on VMs is very fast

Cons:
-can't do bootcamp, as four bays are now taken, and bootcamp can't read the mac software raid (which is also true for hardware raid)
-I'm partitioned as one big drive - but I'm mirrored and backup important data to a home server and use foldershare
-windows games suck in a vm
-raid 0 is much faster with four disks

Check out this thread: https://forums.macrumors.com/threads/266328/

I'm pretty content...
 
If I backup my single hard drive using Time Machine and then reinstall and do RAID 0, can I restore my computer with my backed up settings even though they were not created under a RAID setup?
 
c073186 said:
If I backup my single hard drive using Time Machine and then reinstall and do RAID 0, can I restore my computer with my backed up settings even though they were not created under a RAID setup?
Click to expand...

Of course you can.
 
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