On Fri, Apr 2, 2010 at 9:37 AM, walt <w41...@gmail.com> wrote: > On 04/02/2010 07:59 AM, Mark Knecht wrote: > >> >> 1) Yes, you can RAID partitions of drives. That's what I'm doing. You >> can look at the Gentoo RAID/LVM Install guide to see an example of >> using RAID0 and RAID1 on a single drive. >> >> http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml > > Very useful post, thanks. I'm just nitpicking here about the use of > RAID0 on a single physical drive, which doesn't seem useful IIUC. > > RAID0 alternates stripes between two physical drives so that one disk > can be reading/writing while the other disk's heads are seeking, no? > > If that is the case, then single-disk RAID0 will just be thrashing the > heads back and forth between stripes on different partitions, making > more work for itself than necessary. > > If I'm wrong about this, someone please correct me.
No, you are correct, RAID0 on a single drive makes no sense. If I suggested that then I apologize for the confusion. I was only saying that you can do RAID on one partition but do non-RAID on another. For instance, /boot is non-RAID and then other partitions are RAID. I may be wrong but I think that's only possible with software RAID. Not sure you could do this behind a hardware RAID controller. sda1 = /boot - non-RAID sda2, sdb2, sdc2 = swap, but not RAID. The kernel binds them. sda3, sdb3, sdc3 = RAID /home or something like that. In case even that's not clear, I don't think mdadm supports a RAID array of any type with all the partitions on a single drive. For instance: mdadm --create /dev/md1 --level=1 --raid-devices=3 /dev/sda1 /dev/sda2 /dev/sda3 doesn't make any sense to me even if it is supported. Hope that helps clear things up. ;-) - Mark
