RAID Questions

slabbius

macrumors member
Original poster
Aug 7, 2006
86
0
I'm ordering my MacPro next week and had a few questions about RAID setups. My Idea is to have two WD 500GB Drives in a RAID (1 or 0) and two WD Raptor 150GB either in RAID (1 or 0) or as the first as my system drive and the other as my scratch disk. Any comments on which would be best? Or does anyone else have some good suggestions?
 

Apple2Mac

macrumors regular
Sep 3, 2006
108
0
I run raids in all my desktop machines I run a RAID 0 (striped in all my machines that I run Photoshop or FCP on, it does make a very nice speed difference. I also run my own Mac OS X Server and I have a RAID 1 in it for data reliability and increased read performance.

RAID 0 does have a huge drawback with data reliability, basically because you are using 2 hard disks your hard drive is twice as likely to fail. In the 6 years I've been running RAIDs I have only one had a drive fail that was part of a Striped set. If you do Strip make sure to perform nightly backups of all important data... I use a third external drive for all back ups and also use .mac for backups of critical files...
 

Altimeter88

macrumors member
Jul 17, 2006
99
0
Apple2Mac said:
RAID 0 does have a huge drawback with data reliability, basically because you are using 2 hard disks your hard drive is twice as likely to fail. In the 6 years I've been running RAIDs I have only one had a drive fail that was part of a Striped set. If you do Strip make sure to perform nightly backups of all important data... I use a third external drive for all back ups and also use .mac for backups of critical files...
Actually statistically you have 1/2 the chance of your data failing because each drive is being used 50% less, this is based on the MTBF numbers of course but yeah in real world terms on consumer drives, plan on making backups when running RAID 0.

I have ran RAID 0 setups for the past 5 years and have never had a failure. I am trying to decide if I want to do RAID 0 or RAID 10 on my Mac Pro that is arriving tomorrow. I have 4x500GB new drives and 2TB is sounding a lot better than 1TB but data loss and downtime is never fun.

What Apple really needs to do is get hardware RAID 5 working on the Mac Pro since this is a feature natively supported on the board's Southbridge.
 

Apple2Mac

macrumors regular
Sep 3, 2006
108
0
Altimeter88 said:
Actually statistically you have 1/2 the chance of your data failing because each drive is being used 50% less, this is based on the MTBF numbers of course but yeah in real world terms on consumer drives....
That is completely untrue, Quote from wikipedia
"the reliability of a given RAID 0 set is equal to the average reliability of each disk divided by the number of disks in the set. That is, reliability (as measured by mean time to failure (MTTF) or mean time between failures (MTBF) is roughly inversely proportional to the number of members—so a set of two disks is roughly half as reliable as a single disk."
full text:
http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks
 

slabbius

macrumors member
Original poster
Aug 7, 2006
86
0
well thank you for answers, but i think i'm going to go with this config:

HD1 - 150gb Raptor - System drive
HD2 - 150gb raptor - scratch disk
hd3 and 4 are each 500gb that will be in RAID 1

Maybe a 1TB Buffalo NAS on Raid 5 too


Can't wait to order
 

stevo86

macrumors member
Mar 20, 2006
90
0
Newfoundland, Canada
stupid questions... i know...

How would I even set up a RAID 0?? Also, do you need to use the same drives in a RAID 0, ex: 2x 500GB Western Digital... or would something like 1x 250GB Seagate and 1x 320GB Western Digital work??

sorry for these stupid questions but the whole RAID conecpt is very new to me and it seems pretty interesting.
 

Terrabit

macrumors newbie
Aug 26, 2006
25
0
Suggested RAID Configuration

slabbius said:
I'm ordering my MacPro next week and had a few questions about RAID setups. My Idea is to have two WD 500GB Drives in a RAID (1 or 0) and two WD Raptor 150GB either in RAID (1 or 0) or as the first as my system drive and the other as my scratch disk. Any comments on which would be best? Or does anyone else have some good suggestions?
I have put up my 4 drive, RAID-10 & RAID-0 configurations on the website:

http://www.macprojournal.com/partitions.html

You might find it interesting. I also perform some basic harddrive benchmarks of the different RAID configurations for speed comparison purposes.

Terrabit!
 

UnixMac

macrumors 6502
Oct 1, 2002
326
0
Phoenix, AZ
Many ways to skin the cat, but I opted for a basic 74GB boot Raptor, and 3x500GB in the other bay's with 2 in RAID0... I bought the IBM/Hitatchi 16MB Buffered 500's as they're the fastest 500's I could find on the market, and most reliable.

All told, about $900 spent on drives.. not bad when you consider my 10MB Hard drive on the IBM XT back in 1982 cost me $1450 in 1982 dollars!
 

rtharper

macrumors regular
Sep 6, 2006
203
0
Oxford, UK
Sooo, speaking of RAID. There's hardware RAID 0,1, and 5 on the Woodcrest motherboard. Why doesn't Apple use it?!
 

Apple2Mac

macrumors regular
Sep 3, 2006
108
0
stevo86 said:
How would I even set up a RAID 0?? Also, do you need to use the same drives in a RAID 0, ex: 2x 500GB Western Digital... or would something like 1x 250GB Seagate and 1x 320GB Western Digital work??
You need to use two drives of the same size both 250GB, and it is not required but highly recommended to use two identical drives same manufacture and model number..

To build a raid you run Disk Utility and select two unformatted drives and then go to the RAID tab to select the type of RAID and build it...
 

Terrabit

macrumors newbie
Aug 26, 2006
25
0
Felxability

slabbius said:
well thank you for answers, but i think i'm going to go with this config:

HD1 - 150gb Raptor - System drive
HD2 - 150gb raptor - scratch disk
hd3 and 4 are each 500gb that will be in RAID 1

Maybe a 1TB Buffalo NAS on Raid 5 too

Can't wait to order
Don't forget tat you can have RAID0, RAID1 and RAID10 on the same set of drives. So you could raid-1 for your system drive and raid-0 for your scratch drive (over the two 150gb drives).

Detailed suggestions on how you can achive this are on my website link above in my previous post.

Terrabit!
 

Origin

macrumors regular
Aug 11, 2006
115
0
Nantes, France
Yes, it's definitly a great suggestion. RAID1 for the OS and RAID0 for the scratch, both on the same drives ;)

As anyone compared the performance of the RAID1 over RAID0 (my current setup) on Mac OS X ?

Because, i don't really need 400 Gb for my OS partition, so, I did RAID0 for best performance, but, now I wonder if the RAID1 solution would not be, speed speaking, great too ;)
 

disconap

macrumors 68000
Oct 29, 2005
1,800
2
Portland, OR
Apple2Mac said:
That is completely untrue, Quote from wikipedia
"the reliability of a given RAID 0 set is equal to the average reliability of each disk divided by the number of disks in the set. That is, reliability (as measured by mean time to failure (MTTF) or mean time between failures (MTBF) is roughly inversely proportional to the number of members—so a set of two disks is roughly half as reliable as a single disk."
full text:
http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks
Haha, sorry, you may very well be right, but realize that you are trying to use WIKIPEDIA as your source. Wikipedia is not a reliable source of anything, it's just a good starting point.
 

UnixMac

macrumors 6502
Oct 1, 2002
326
0
Phoenix, AZ
disconap said:
Haha, sorry, you may very well be right, but realize that you are trying to use WIKIPEDIA as your source. Wikipedia is not a reliable source of anything, it's just a good starting point.
I actually disagree on that... I've rarely read anything "not reliable" on Wikipedia, and I do a LOT of reading..

It's an old wives tale that's no longer valid... the policing of Wikipedia is much better now.
 

patseguin

macrumors 68000
Aug 28, 2003
1,552
447
Can I add another 250GB drive to my Mac Pro and created a RAID or will I have to wipe the existing drive?
 

Origin

macrumors regular
Aug 11, 2006
115
0
Nantes, France
For the RAID0 or RAID5 its mandatory to re-format.

For the RAID1, I don't known, but, if it's software... there is a possibility that Mac OS X might accept to "upgrade" a single disk to a mirror without reformatting ... look in the disk utility panel ;)
 

disconap

macrumors 68000
Oct 29, 2005
1,800
2
Portland, OR
UnixMac said:
I actually disagree on that... I've rarely read anything "not reliable" on Wikipedia, and I do a LOT of reading..

It's an old wives tale that's no longer valid... the policing of Wikipedia is much better now.
Sorry, but I just don't trust any source that will allow me to edit it. ;)
 

Terrabit

macrumors newbie
Aug 26, 2006
25
0
Origin said:
For the RAID0 or RAID5 its mandatory to re-format.

For the RAID1, I don't known, but, if it's software... there is a possibility that Mac OS X might accept to "upgrade" a single disk to a mirror without reformatting ... look in the disk utility panel ;)
Unfortunately, while it is possible to mirror a volume under Windows XP without destroying the master, its not possible to do that trick with Disk Utility.

The disk-management side of OS X is still a little-bit behind.

I suspect they put all there energy into their high-value SAN product, rather than optimising the underlying operating system. I hope they improve the file system handling in the next major release.

Terrabit!
 

Apple2Mac

macrumors regular
Sep 3, 2006
108
0
There is a way to turn a single disk into a Raid 1, but it requires the command line and editing partition information. (if you were to make a mistake it would destroy all information on your drive) Try searching macosxhints.com I think that is where it was posted..