Thanks John! On Thu, Feb 26, 2015 at 1:12 PM, John Dickinson <m...@not.mn> wrote: > Well, it's complicated ;-) > > Start with http://docs.openstack.org/developer/swift/overview_ring.html > > > Think about your scenario. if you have differently sized failure domains, > then there are 2 options: limit capacity to the smallest failure domain or > have some capacity overweighted (ie more than one replica there). Both of > these are reasonable and have different tradeoffs. > > If you deploy your Swift cluster so that you have evenly sized failure > domains (regions, zones, servers), then things will "just work" exactly as > you expect it to. If you don't have even failure domains, then you'll have to > figure how much you want to accept overweighted failure domains (more than > the expected number of replicas in a failure domain). > > There is a "knob" in Swift you can turn to configure this choice: overload. > See the docs linked above for info on it. Also, The swift-ring-builder also > now includes a "dispersion" command so you can see if your cluster is set up > to have overweighted failure domains. > > > --John > > > > > >> On Feb 26, 2015, at 12:40 PM, Shrinand Javadekar <shrin...@maginatics.com> >> wrote: >> >> Hi, >> >> I have a question about using unevenly sized disks in a Swift cluster >> configured to do 2x replication. >> >> Let's say I start with two disks of 10GB each and configure the rings >> so that both the disks have the same weight (say 10). In this case, >> one replica of each object will be on each device. >> >> At a later point, I increase the capacity of the cluster by adding one >> 500GB disk. I also assign it a weight 500. >> >> This means that my 500GB disk should have 50x more data than the 10GB >> ones. Swift will move some replicas of existing objects onto this >> 500GB disk. >> >> How does Swift place data such that it the "as unique as possible" >> policy is maintained. Beyond a point, won't it have to place both >> replicas on the same device (the 500GB disk)? >> >> If yes, to overcome the above problem, does Swift recommend always >> adding a pair of evenly sized disks (for 2x replication)? >> >> Thanks in advance. >> -Shri >> >> _______________________________________________ >> Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack >> Post to : openstack@lists.openstack.org >> Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack >
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