I haven't looked at the internals of the model, but the PL(site) you've pointed out is definitely the crux of the issue here. In the first grouping, it's just looking at the probability of data loss due to failing disks, and as the copies increase that goes down. In the second grouping, it's including other factors like the entire data center getting knocked out. That possibility is greater than losing data due to three disk failures here, so it's capping the total data durability. -Greg On Sat, Aug 22, 2015 at 2:38 AM, dahan <dahanhsi@xxxxxxxxx> wrote: > Hi, > I have crosspost this issue here and in github, > but no response yet. > > Any advice? > > On Mon, Aug 10, 2015 at 10:21 AM, dahan <dahanhsi@xxxxxxxxx> wrote: >> >> >> Hi all, I have tried the reliability model: >> https://github.com/ceph/ceph-tools/tree/master/models/reliability >> >> I run the tool with default configuration, and cannot understand the >> result. >> >> ``` >> storage durability PL(site) PL(copies) PL(NRE) >> PL(rep) loss/PiB >> ---------- ---------- ---------- ---------- ---------- >> ---------- ---------- >> Disk: Enterprise 99.119% 0.000e+00 0.721457% 0.159744% >> 0.000e+00 8.812e+12 >> RADOS: 1 cp 99.279% 0.000e+00 0.721457% 0.000865% >> 0.000e+00 5.411e+12 >> RADOS: 2 cp 7-nines 0.000e+00 0.000049% 0.003442% >> 0.000e+00 9.704e+06 >> RADOS: 3 cp 11-nines 0.000e+00 5.090e-11 3.541e-09 >> 0.000e+00 6.655e+02 >> ``` >> >> ``` >> storage durability PL(site) PL(copies) PL(NRE) >> PL(rep) loss/PiB >> ---------- ---------- ---------- ---------- ---------- >> ---------- ---------- >> Site (1 PB) 99.900% 0.099950% 0.000e+00 0.000e+00 >> 0.000e+00 9.995e+11 >> RADOS: 1-site, 1-cp 99.179% 0.099950% 0.721457% 0.000865% >> 0.000e+00 1.010e+12 >> RADOS: 1-site, 2-cp 99.900% 0.099950% 0.000049% 0.003442% >> 0.000e+00 9.995e+11 >> RADOS: 1-site, 3-cp 99.900% 0.099950% 5.090e-11 3.541e-09 >> 0.000e+00 9.995e+11 >> >> ``` >> >> The two result tables have different trend. In the first table, durability >> value is 1 cp < 2 cp < 3 cp. However, the second table results in 1 cp < 2 >> cp = 3 cp. >> >> The two tables have the same PL(site), PL(copies) , PL(NRE), and PL(rep). >> The only difference is PL(site). PL(site) is constant, since number of site >> is constant. The trend should be the same. >> >> How to explain the result? >> >> Anything I missed out? Thanks >> > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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