If you had 5 raw disks raid0 is faster, but with the separate partition setup linear will be faster because linear does not have a seek from one partition to another but instead a linear write. Note that on reads raid5 performs similar to a raid0 stripe of 1 less disk, writes on raid5 Based on those messages The re-add would be expected to work fine. it appears that the machine was shutdown wrong and/or crashed and kicked the devices out because the data was a few events behind on that device. I have seen this happen from time to time. In general the re-add will do the right thing or will get an error. When something goes wrong you always need to check messages and see what the underlying issue is/was. Find any lvm instruction and treat the N mdraids as "disks" but and do not do stripe (the simple default will do what you want) and the default method lvm uses will lay out the new block devices as one big device basically using all of the first raid and then the next one and so on. or you can simply recreate the big device and specific an mdadm type of "linear" rather than raid0. On Thu, Nov 24, 2022 at 4:03 PM Wol <antlists@xxxxxxxxxxxxxxx> wrote: > > On 24/11/2022 21:10, David T-G wrote: > > How is linear different from RAID0? I took a quick look but don't quite > > know what I'm reading. If that's better then, hey, I'd try it (or at > > least learn more). > > Linear tacks one drive on to the end of another. Raid-0 stripes across > all drives. Both effectively combine a bunch of drives into one big drive. > > Striped gives you speed, a big file gets spread over all the drives. The > problem, of course, is that losing one drive can easily trash pretty > much every big file on the array, irretrievably. > > Linear means that much of your array can be recovered if a drive fails. > But it's no faster than a single drive because pretty much every file is > stored on just the one drive. And depending on what drive you lose, it > can wipe your directory structure such that you just end up with a > massive lost+found directory. > > That's why there's raid-10. Note that outside of Linux (and often > inside) when people say "raid-10" they actually mean "raid 1+0". That's > two striped raid-0's, mirrored. > > Linux raid-10 is different. it means you have at least two copies of > each stripe, smeared across all the disks. > > Either version (10, or 1+0), gives you get the speed of striping, and > the safety of a mirror. 10, however, can use an odd number of disks, and > disks of random sizes. > > Cheers, > Wol
