Jose Luis Domingo Lopez <linux-raid@24x7linux.com> writes: > On Wednesday, 07 January 2004, at 01:37:20 +0100, > Måns Rullgård wrote: > >> I recently created a RAID1 mirror from two identical RAID0 arrays >> under Linux 2.6.0. I was surprised when /proc/mdstat reported a >> resync speed of 1 MB/s, even though the system was otherwise idle. I >> > Anyways, it seems wiser to make two RAID1 arrays and then a RAID0 from > them two. Apart from (maybe) preventing the problem you are > experiencing, this should give you better results in the case of a drive > failure, when it happens. > > Think for a moment about the event of a single hard drive failure: with > two RAID1 arrays, one of then will go to degraded mode, but as far as I > know the upper RAID0 will not notice a thing, so will continue working > as usual, maybe with a little performance decrease. > > On the other hand, if you have two RAID0 arrays and one of the hard > drives fail, the RAID0 where it happens will fail, the upper RAID1 will > run degraded, and when a new disk replaces the failed one you will have > to start the failed RADI0 again, and let the upper RAID1 reconstruct > itself. I think this situation is worse than the one depicted before. > > Am I missing something ? I had a few reasons: - I read somewhere that RAID0 over RAID1 didn't work. Maybe this information was outdated. - I was short on spare disks, so I had to build an initially degraded array and then add the other half of the mirror. - Performance after a disk failure isn't a big issue with this machine. Resyncing takes only an hour or two anyway. -- Måns Rullgård mru@kth.se - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
