Raid Level 8 ??

[Samsonid]

Hi,

After putting some thought on a previous discussion about the various Raid levels, and after reading the information on the StorageReview.com....
...it occured to me that we may need one more Raid level (say level 8) ?

Particularly:
This level will perform just like a Raid 1+0 but with only 3 disks
The requirement is that two disks are *identical* (say 40Gb) and the third disk is double (say 80Gb)
The two small disks are in Raid0 and they are mirrored against the 80Gb large disk.
(the large disk should not be partitioned...partitioning will fragment the data and slow performance)

Any thoughts about this?
Any "culprits" in performance ?
Is this already possible ? (maybe something I missed)?

Thanks

 

[ViRGE]

I can't particularly see a use for it. RAID 5 would use all 3 disks at once, increasing drive performance, so this would really only be a "limbo" solution for people that want 5, but can't really move past 0+1. That said, I'd be surprised if it worked, since the RAID specs always call for disks of the same capacity; something like this would be really screwy, and probably require a co-processor to help the RAID system figure out where to go to get/put data.

 

[Cerb]

I agree with ViRGE...RAID 5 already works just fine for three disks.

 

[AgaBoogaBoo]

There is one problem with your idea. You would have to make the 80GB drive twice as fast as the two 40GB's in Raid 0 because it has to mirror them at their speed.

 

[sharkeeper]

There is one problem with your idea. You would have to make the 80GB drive twice as fast as the two 40GB's in Raid 0 because it has to mirror them at their speed.

Interleaving, dynamic wait states, and adaptive algorithms are your friend.

Of course this does nothing to improve performance.

-DAK-

 

[AgaBoogaBoo]

Originally posted by: shuttleteam

There is one problem with your idea. You would have to make the 80GB drive twice as fast as the two 40GB's in Raid 0 because it has to mirror them at their speed.

Interleaving, dynamic wait states, and adaptive algorithms are your friend.

Of course this does nothing to improve performance.

-DAK-

Wow, a second post in 10 minutes I reply to of yours and I hardly know what you're talking about. Actually, this t ime I think I have an idea.

By Dyanmic wait stages do you mean for the 80GB drive to "catch up" and basically keep writing till it is in sync with the other drives. I guess by adaptive algorithms you mean something that uses algorithms to simplify the writing of data and so it can keep up.

Implementing some like that would be a PITA, wouldn't it? Oh yeah, I have no clue what you mean by interleaving except for the "inter" prefix which in etymology I learned means "between."

 

[sharkeeper]

Yes as it's kind of hard to pull the stuff out of the bag faster than you can fill it. (works both ways here) I suppose one can buffer the stuff but misses will cause severe penalties in performance. After all, RAID is about performance!

PITA? Yes in most cases, but it's hard to have gain without feeling the pain. That's what us engineers are for!

-DAK-