RAID inquiry

[Lonyo]

I remember reading a thing about RAID 1.5 and it seemed to basically be a load of rubbish.

I was wondering about RAID 0+1 though. I know it's striping and mirroring, and the speed of the drives is almost double that of a single drive because the data can be written/read from the 2 striped drives concurrently. The other 2 drives then mirror what's on the first 2 drives.

In this 4 drive setup, could you not have all 4 drives acting in a way together, so you could write/read to and from all 4 at the same time, so drive 1 gets A, drive 2 gets B drive 3 gets C and drive 4 gets D, so you have 4 times the write speed, and then drives 1&2 have C&D copied to them a bit after and vice versa, so you get all the data mirrored, but it can be written and read even faster.

Would that even be possible? I don't know if I really explained what I mean but hopefully someone might get it.

 

[Pas2002]

i think what you are talking about is Raid 5
i dont have a url for you but if you just search for raid 5 you will get more then enough info.

 

[GRIFFIN1]

As far as I know, RAID 1 would be able to read from all for drives, but it writes, it is only as fast as writing to two drives. If it "waited" slack time to finish writing, then you would be in trouble if the power went out.

RAID 5 would only need 3 drives, but I think it is slower.

 

[SCSIRAID]

RAID 01 and 10 are heirarchial arrays. 01 is a striped set made up of two RAID 1 sets. Consider 4 drives broken into two mirrored pairs. Then stripe the data across the mirrored pairs. 10 is the opposite. Take 4 drives and create two striped sets. Then mirror them. One nice thing about 10 is the ability to break the set and end up with a 'clone' since the two RAID 0 sets are identical (since they are mirrored).