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Two RAID drives on only two hard disks...

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a b G Storage
February 14, 2008 12:37:59 PM

I like the performance RAID 0 and security of RAID 1.
Wouldn’t be wise to buy two high performance sata drives (let’s say Seagate Barracuda 7200.11 – 500gb – 105 mb/sec data rate…) and partition each to 25 and 475 gb. You can then form RAID 0 on the two 25 gb drives and use that partition for operating system+programs boot drive (50 gb total). And then form RAID 1 with the remaining two 475 gb partitions and use that drive for documents, etc data. Two hard disks and two RAID drives… One for fast boot and the other for safe data…
What do you think? Is this a good idea?

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February 14, 2008 12:49:41 PM

It's such a good idea, it's already been implemented. Intel calls this "Matrix Raid" and supports it on their RAID-enabled chipsets.
a b G Storage
February 14, 2008 1:14:38 PM

Thank you for the information. I didn't know what "matrix raid" is... I had ignorantly thought it's just a fancy name Intel coined... :) 

Actually I do have my boot drive on two 80 gb RAID 0 and my data on two 500 gb RAID 1, plus one other 500 gb (single) is my backup disk. I was thinking of replacing my boot drives with new and faster drives. The problem seems to be the fastest drives seem to start with 500 gb., a capacity I don't need... Guess I can use the rest for additional backup or other data space…
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February 14, 2008 1:44:07 PM

Try Matrix Raid you'll like it. You can adjust Raid 0 & Raid 1 to custom sizes to what ever fits your needs. The great thing is that it is transportable to other Intel (RAID)Chipset Moptherboards.
a b G Storage
February 14, 2008 3:10:27 PM

Yes, its called RAID 0+1 or Matrix RAID. However, RAID 0 gives performance benefits because 2 physical drives are working at the same time to read and write data.. much like 2 people painting a house, effectively doubling the speed. Matrix RAID basically eliminates all speed advantages of RAID 0 because the hard drives are also writing the mirrored part of the data at the same time, so its basically worthless.

RAID 0 is like 2 painters painting a house, using both hands (4 hands painting). RAID 1 would be 1 painter painting the house with both hands and the other painter standing next to him and watching (2 hands painting). RAID Matrix would be like 2 painters painting with 1 hand tied behind thier backs (2 hands painting).
a b G Storage
February 14, 2008 3:57:18 PM

Cirdecus,
I had thought RAID 0+1 was a RAID 0 pair mirrored by another RAID 0 set. That is having the best of both worlds: RAID 0 performance at RAID 1 safety. Penalty is having to utilize 4 hard disks.

But what I propose different. In that case boot RAID 0 is not mirrored, it does not have any of the safety of RAID 1 partition. But the data section is RAID 1

February 14, 2008 4:34:47 PM

If a drive fails and Matrix RAID can rebuild just the partition of the good drive, or treat partition of the good drive as a stand alone drive, then it is a pretty good set up. BTW as long as there is nothing going on across the partitions then the performance will be close to RAID 0 for R/W. The controller may slow things down some vs. as standalone RAID 0. Anything read from the RAID 1 partion will be nearly as fast as RAID 0, the writes will be at standard speed. Any cross partition R/W will probably slow both drives down to close to standard speeds and give the controller and drives a real workout.
February 14, 2008 4:35:16 PM

Kursun,
it doesn't really matter if RAID 0 on such an array is not mirrored because both arrays exist on the same physical drive. So the drives must be doing all the work to keep both RAID 0 and 1 synced at the same time, so it's like doing twice the work, negating the benefits of having that RAID 0 array on there in the first place.

I haven't personally tested such a setup yet though, so I can't comment on how much that would affect performance. I'm sure you can find a review of Matrix Raid somewhere.
February 14, 2008 7:51:51 PM

cirdecus said:
Yes, its called RAID 0+1 or Matrix RAID. However, RAID 0 gives performance benefits because 2 physical drives are working at the same time to read and write data.. much like 2 people painting a house, effectively doubling the speed. Matrix RAID basically eliminates all speed advantages of RAID 0 because the hard drives are also writing the mirrored part of the data at the same time, so its basically worthless.

RAID 0 is like 2 painters painting a house, using both hands (4 hands painting). RAID 1 would be 1 painter painting the house with both hands and the other painter standing next to him and watching (2 hands painting). RAID Matrix would be like 2 painters painting with 1 hand tied behind thier backs (2 hands painting).


Not at all correct. Matrix RAID and RAID 0+1 are two completely different and separate things.

RAID 0+1 is a nested RAID level that builds two separate mirrored RAID sets and then stripes data across them. The result appears as one virtual drive.

Matrix RAID is a mechanism where you can have a RAID 0 array and a completely separate RAID 1 array (which normally would require 4 disks) but instead only 2 disks are used. The result is two virtual drives, one that is RAID 0 and one that is RAID 1.

pkquat said:
If a drive fails and Matrix RAID can rebuild just the partition of the good drive, or treat partition of the good drive as a stand alone drive, then it is a pretty good set up. BTW as long as there is nothing going on across the partitions then the performance will be close to RAID 0 for R/W. The controller may slow things down some vs. as standalone RAID 0. Anything read from the RAID 1 partion will be nearly as fast as RAID 0, the writes will be at standard speed. Any cross partition R/W will probably slow both drives down to close to standard speeds and give the controller and drives a real workout.


Matrix RAID can indeed rebuild the RAID 1 section on a drive failure. The data on the RAID 0 section is lost (as it ordinarily would be when a drive fails). The RAID 0 section does not suffer any performance hit. The RAID 1 section will have read and write speeds approximately equal to that of a single drive, the Intel chipset does not have the ability to increase RAID 1 read speed - it is not as intelligent as enterprise-level RAID controllers which typically can. Be careful of the terminology you use here - the two different sections of the drives are not partitions - partitions are file-system level entities. The sections that comprise the different RAID areas are logical volumes.

evilshuriken said:
Kursun,
it doesn't really matter if RAID 0 on such an array is not mirrored because both arrays exist on the same physical drive. So the drives must be doing all the work to keep both RAID 0 and 1 synced at the same time, so it's like doing twice the work, negating the benefits of having that RAID 0 array on there in the first place.

I haven't personally tested such a setup yet though, so I can't comment on how much that would affect performance. I'm sure you can find a review of Matrix Raid somewhere.


The RAID 0 section and RAID 1 section don't have anything to do with each other, and don't "sync". The RAID 0 section performs as a RAID 0 drive would, and the RAID 1 section performs as a RAID 1 drive would.
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