2016-03-06 22:49 GMT+08:00 Richard Elling <[email protected]> :
> > On Mar 3, 2016, at 8:35 PM, Fred Liu <[email protected]> wrote: > > Hi, > > Today when I was reading Jeff's new nuclear weapon -- DSSD D5's CUBIC RAID > introduction, > the interesting survey -- the zpool with most disks you have ever built > popped in my brain. > > > We test to 2,000 drives. Beyond 2,000 there are some scalability issues > that impact failover times. > We’ve identified these and know what to fix, but need a real customer at > this scale to bump it to > the top of the priority queue. > > [Fred]: Wow! 2000 drives almost need 4~5 whole racks! > > For zfs doesn't support nested vdev, the maximum fault tolerance should be > three(from raidz3). > > > Pedantically, it is N, because you can have N-way mirroring. > [Fred]: Yeah. That is just pedantic. N-way mirroring of every disk works in theory and rarely happens in reality. > > It is stranded if you want to build a very huge pool. > > > Scaling redundancy by increasing parity improves data loss protection by > about 3 orders of > magnitude. Adding capacity by striping reduces data loss protection by > 1/N. This is why there is > not much need to go beyond raidz3. However, if you do want to go there, > adding raidz4+ is > relatively easy. > [Fred]: I assume you used stripped raidz3 vedvs in your storage mesh of 2000 drives. If that is true, the possibility of 4/2000 will be not so low. Plus, reslivering takes longer time if single disk has bigger capacity. And further, the cost of over-provisioning spare disks vs raidz4+ will be an deserved trade-off when the storage mesh at the scale of 2000 drives. Thanks. Fred > > > -- > > [email protected] <[email protected]> > +1-760-896-4422 > > > > *openzfs-developer* | Archives > <https://www.listbox.com/member/archive/274414/=now> > <https://www.listbox.com/member/archive/rss/274414/28015160-28f9d00e> | > Modify > <https://www.listbox.com/member/?&;> > Your Subscription <http://www.listbox.com> > ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
