> 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 > <mailto:richard.ell...@richardelling.com>>: > >> On Mar 3, 2016, at 8:35 PM, Fred Liu <fred_...@issi.com >> <mailto: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. -- richard ------------------------------------------- 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
