Casey Bodley <cbodley@xxxxxxxxxx> 于2018年8月29日周三 下午8:24写道： > > > On 08/29/2018 02:33 AM, Test Test wrote: > > Hi cephers: > > > > Recently, I was testing the multisite of rgw(ceph 12.2.5). I have some > > questions, can you give me a hand? > > > > 1. every zone has its own placement-rules. But when I create a bucket, > > it will be created on all the other zones which requires the zone s > > have the same placement-rule. So are the placement rules the zone's > > info or the zonegroup's info? > > the set of possible placement rules are defined in the zonegroup. each > zone needs to map each of those placement rules to its own pool names. > so there's both a global (zonegroup) part and a local (zone) part > > > 2. every bucket records its placement-rule and it asks the > > placement-rule never changed. But we can change the placement-rule > > easily. So why does not the bucket record the pool's info instead of > > the placement-rule? > > all bucket metadata (which includes this placement id) is replicated > between zones by metadata sync, so is effectively global. the pool names > themselves are local to zones, because different zones want to use > different pools. that wouldn't work if the bucket stored the pool names > directly > > in fact, before jewel the bucket did store pool names - and we still > support the 'explicit_placement' field for backward compatibility, > though it has that defect when used in a multisite configuration > > > > > 3. the zonegroup has a default placement-rule. Why is the default > > placement-rule zonegroup-level, not zone-level? > > > > Thanks!!! > > the default placement rule is used when creating new buckets, and all > bucket creation happens on the metadata master zone (the master zone of > the master zonegroup). if that zone becomes unavailable and you fail > over to another master zone, it should use that same default The list of placement-rules is global and the content of placement-rules is local. After a bucket uses the placement-rule, the placement-rule should not be changed again. If we modify as follows: 1. When a bucket is created, it records the placement-rule and pools' info( in 'explicit_placement'). 2. When a bucket syncs, the plcament-rule syncs, the pools' info does not sync. the bucket in other zones updates its pools‘ info (according the placement-rule in other zones). So the bucket in different zones will have the same placement-rule but different pools' info. And changing the placement-rule will not affect the availability of the bucket.
