IBR feature works in CE in build 3.0.0-520

Install couchbase server community version 3.0.0-520
Go through initial setup to create default bucket (1 replica)
Load 10K items to bucket
Do cbbackup to backup, got full backup
done
[root@centos-64-x64 ~]# /opt/couchbase/bin/cbbackup http://127.0.0.1:8091 /backup/backup-2
################### 100.0% (10000/estimated 10000 msgs)
bucket: default, msgs transferred...
: total | last | per sec
byte : 100000 | 100000 | 40088.2
done

[root@centos-64-x64 ~]# ls /backup/backup-2/2014-03-27T215707Z/
2014-03-27T215707Z-full

Load 10K items more with different keys.
Run cbbackup one more time, got differential backup

[root@centos-64-x64 ~]# /opt/couchbase/bin/cbbackup http://127.0.0.1:8091 /backup/backup-2
########## 55.1% (11024/estimated 20000 msgs)
bucket: default, msgs transferred...
: total | last | per sec
byte : 110240 | 110240 | 10231.6
done

There is a *diff directory with data in it.
[root@centos-64-x64 ~]# ls /backup/backup-2/2014-03-27T215707Z/
2014-03-27T215707Z-full 2014-03-27T215819Z-diff

[root@centos-64-x64 ~]# ls -hl /backup/backup-2/2014-03-27T215707Z/2014-03-27T215819Z-diff/bucket-default/node-127.0.0.1%3A8091/
total 684K
rw-rr-. 1 root root 678K Mar 27 14:58 data-0000.cbb
rw-rr-. 1 root root 124 Mar 27 14:58 meta.json