2016-03-07 14:04 GMT+08:00 Richard Elling <richard.ell...@gmail.com>:
> > On Mar 6, 2016, at 9:06 PM, Fred Liu <fred.f...@gmail.com> wrote: > > > > 2016-03-06 22:49 GMT+08:00 Richard Elling < > richard.ell...@richardelling.com>: > >> >> On Mar 3, 2016, at 8:35 PM, Fred Liu <fred_...@issi.com> 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. > > > Please don't assume, you'll just hurt yourself :-) > For example, do not assume the only option is striping across raidz3 > vdevs. Clearly, there are many > different options. > [Fred]: Yeah. Assumptions always go far way from facts! ;-) Is designing a storage mesh with 2000 drives biz secret? Or it is just too complicate to elaborate? Never mind. ;-) Thanks. Fred > > *smartos-discuss* | Archives > <https://www.listbox.com/member/archive/184463/=now> > <https://www.listbox.com/member/archive/rss/184463/22027488-c60da3c5> | > Modify > <https://www.listbox.com/member/?&;> > Your Subscription <http://www.listbox.com> > ------------------------------------------- openzfs-developer Archives: https://www.listbox.com/member/archive/274414/=now RSS Feed: https://www.listbox.com/member/archive/rss/274414/28015062-cce53afa Modify Your Subscription: https://www.listbox.com/member/?member_id=28015062&id_secret=28015062-f966d51c Powered by Listbox: http://www.listbox.com
