On 09/09/18 16:32, Wilson Jonathan wrote: > I've tried to google, but its not being my friend as I may be using the > incorrect terms. > > What I'm trying to find out is if I can create a raid10 with six/6 > drives but with a triple mirror where there are only 2 mirrors > containing 3 drives a piece. > > Basically > <-------- raid 0 ---------> > <- raid 1 -> <- raid 1 -> > M1 M1 M1 M2 M2 M2 This is an odd combination. Do you have a particular reason for wanting such a setup? It is not uncommon to build higher level raids on top of mirror pairs, but less common to have three-way mirrors. (Many raid systems don't support three-way mirrors at all. Of course, Linux md raid supports everything :-) ) Raid 5 over pairs gives you better redundancy and can be extended with more pairs if you need it later. <-------- raid 5 --------------> <- r1 -> <- r1 -> <- r1 -> M1 M1 M2 M2 M3 M3 If you want simple layered RAID 0 over RAID 1, that's easy enough to make (as John's post showed). If you want better performance, RAID 10 can be better - as Andreas said, you can do raid10 with "-n3" and six drives. For read-heavy loads on spinning rust disks, raid10 with "-f3" and six drives will give you triple redundancy and /faster/ large streaming reads than a six-drive RAID 0 can achieve (but slower writes). However, RAID 10 layouts can be restrictive if you later want to re-arrange things such as using bigger disks. The "best" solution, as always, depends on the details of your needs and priorities. > > I guess I could manually create two three way mirrors and then manually > create a single stripe over the top... but I'm wondering if mdadm's > raid10 has a way of knowing there should be three copies via an option? > > If mdadm can't create the raid 10, with two three way mirrors, my next > questions are - > > Also how do I tell mdadm to create a three copy raid1? > > Eg. M1 M1 M1 > > Also do I then need to set up the madam.conf file to first have the two > individual three way mirrors followed by the raid 0 over the top? > > eg. > > ARRAY /dev/md/1 UUID=aaaaaa... ## first triple mirror > ARRAY /dev/md/2 UUID=bbbbbb... ## second triple mirror > ARRAY /dev/md/3 UUID=cccccc... ## raid 0 over md/1 & md/2 > > Thanks in advance. > > Jon >
