how to store blobs in hierarchical structure in Centera?

Alex - Centera is an object based storage system. As such, it has no concept of a filesystem or a hierarchy. So you must model what you are looking for within the metadata or the tag structure of the clip.

However, this approach will not work well for a "dynamic" set of data. In other words, you could easily model a directory structure within the structure of a clip - top tag being the root folder, objects within that folder being child tags and so on. The problem comes when you add new files to the structure - this wouild result in changes to the clip being required, which would result in a new content address when the clip was written/persisted after the new tags and files have been added.

The solution in this case would be to delete the old clip and update your database with the new content address. If you had placed a retention value on the clip (which was still relevant i.e. not expired)  then this would require Privileged Delete (and would rule out the possibility of using CE+ clusters as that capability is not available).

So if you do not use retention (or are happy with this restrictions I have mentioned) then you could use this approach. If the data structure is very dynamic (i.e. the clips would require frequent updating) then I would advise caution as each deleted object would leave a Reflection behind and you could exhaust the cluster object count limit.

An alternative solution is to use a file system gateway application/appliance to provide the interface to your application and let it worry about the integration with the Centera. There are many of these available, including the EMC File Management Appliance and ISV applications that work on standard filesystems or NAS devices.

Graham, thanx a lot for your reply.

Actually thats the issue i was facing as you mentioned, mean whenever a new file/blob added into the tag a new clipreference is generated.

Can you explain any other logical solution or some sample code.