On Fri, Feb 04, 2011 at 02:27:38AM -0600, Stan Hoeppner wrote: > Keld Jørn Simonsen put forth on 2/4/2011 1:06 AM: > > > Well RAID1+0 is not the best combination available. I would argue that > > raid10,f2 is significantly better in a number of areas. > > I'd guess Linux software RAID would be lucky to have 1% of RAID deployments > worldwide--very lucky. The other 99%+ are HBA RAID or SAN/NAS "appliances" most > often using custom embedded RTOS with the RAID code written in assembler, > especially in the case of the HBAs. For everything not Linux mdraid, RAID 10 > (aka 1+0) is king of the hill, and has been for 15 years+ Yes, you are right, Linux MD really has an advantage here:-) > >> Something smells bad here. Does one of the RAID companies own a patent or > >> trademark on "RAID 10"? I'll look into this. It just doesn't make any sense > >> for RAID 10 to be omitted from the SNIA DDF but to be referenced in the manner > >> it is. > > > > It looks like they do define all major basic RAID disk layouts. (except > > raid10,f2 of cause) . RAID1+0 is a derived format, maybe that is out of > > scope of the DDF standard. > > "A secondary virtual disk is a VD configured using hybrid RAID levels like > RAID10 or RAID50. Its elements are BVDs." > > So apparently their Disk Data Format specification doesn't include hybrid RAID > levels. This makes sense, as the _on disk_ layout of RAID 10 is identical to > RAID 1. Yes, raid10 is just a variation of RAID1, actually raid10,n2 is identical on the disk to RAID1, eg for a 2 drive or 4-drive array. > We apparently need to be looking for other SNIA documents to find their > definition of RAID 10. That is what started us down this tunnel isn't it? > We're so deep now there's no light and I can't see the path behind me anymore. ;) I dont think SNIA defines RAID 10, which is a specific Linux MD thing. For RAID1+0, I think it is covered by the DDF standard, as what DDF is aimed at is defining formats on the disks to portably handle RAID. That means that you can move a set of disks used in one manufacturer's configuration to another make's configuration, and it will still work. And it will also work with RAID1+0, as the underlying RAID1 and RAID0 formats are defined in DDF. So no need to add specific RAID1+0 definitions. Also RAID1 may mean different layouts, like the "far" and "offset" layouts, and it would mean an explosion of definitions of RAID1+0 if you should name and standardize all of these variations of RAID1+0 explicitely. best regards keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
