Originally Posted by Puwaha
No, FlexRAID is nothing like RAID 3. RAID 3 stripes data across all the drives per byte, with the parity byte on one single disk. RAID 4 stripes data across all the drives on a block level using a single disk to store the parity block.
FlexRAID does block-level parity like in RAID 4, not byte-level parity in RAID 3... So it's closer to RAID 4 than anything else.
I've never seen RAID 3 in use anywhere, as it's pretty inefficient. Having to read a byte at a time sequentially from each disk is very inefficient compared to RAID 4 and 5 where they read whole blocks of data in parallel from all the disks at the same time. I worked at a company that built Video-on-Demand servers back in the mid-90's (way ahead of their time), and they preferred RAID 4 over 5 (writes are very slow, but read speed is excellent on RAID 4, mainly because you don't have to skip the parity block [re-seek the head] on reads like you would in a sequential RAID 5 read.) For serving up multiple large sequential write-once-read-many files like video files, RAID 4 is tops.
You're original post said Flexraid "was essentially Raid 4", and that's not the case. While there are similarities to Raid 4, it's the differences that make Flexraid (and others) attractive alternatives to traditional Raid.
You're latest post above, says "it's closer to Raid 4 than anything else", and that I agree with completely. Didn't want anyone thinking that Flexraid was just Raid 4 under another name, and I don't think you meant to imply that either.
Both Raid 3 and 4 use a single disk to store the parity, and in that sense, both are similar to Flexraid. I'm aware that Raid 3 was seldom (perhaps never) used, but Raid 4 has also virtually disappeared from the landscape.
Again, I wasn't trying to start a fight, I just didn't (don't) agree that Flexraid "is essentially Raid 4".