SNIA CDMI plugfest for cloud storage and cloud data services

Plug by Samuel M. Livingston (cc) (from Flickr)
Plug by Samuel M. Livingston (cc) (from Flickr)

Was invited to the SNIA tech center to witness the CDMI (Cloud Data Managament Initiative) plugfest that was going on down in Colorado Springs.

It was somewhat subdued. I always imagine racks of servers, with people crawling all over them with logic analyzers, laptops and other electronic probing equipment.  But alas, software plugfests are generally just a bunch of people with laptops, ethernet/wifi connections all sitting around a big conference table.

The team was working to define an errata sheet for CDMI v1.0 to be completed prior to ISO submission for official standardization.

What’s CDMI?

CDMI is an interface standard for clients talking to cloud storage servers and provides a standardized way to access all such services.  With CDMI you can create a cloud storage container, define it’s attributes, and deposit and retrieve data objects within that container.  Mezeo had announced support for CDMI v1.0 a couple of weeks ago at SNW in Santa Clara.

CDMI provides for attributes to be defined at the cloud storage server, container or data object level such as: standard redundancy degree (number of mirrors, RAID protection), immediate redundancy (synchronous), infrastructure redundancy (across same storage or different storage), data dispersion (physical distance between replicas), geographical constraints (where it can be stored), retention hold (how soon it can be deleted/modified), encryption, data hashing (having the server provide a hash used to validate end-to-end data integrity), latency and throughput characteristics, sanitization level (secure erasure), RPO, and RTO.

A CDMI client is free to implement compression and/or deduplication as well as other storage efficiency characteristics on top of CDMI server characteristics.  Probably something I am missing here but seems pretty complete at first glance.

SNIA has defined a reference implementations of a CDMI v1.0 server [and I think client] which can be downloaded from their CDMI website.  [After filling out the “information on me” page, SNIA sent me an email with the download information but I could only recognize the CDMI server in the download information not the client (although it could have been there). The CDMI v1.0 specification is freely available as well.] The reference implementation can be used to test your own CDMI clients if you wish. They are JAVA based and apparently run on Linux systems but shouldn’t be too hard to run elsewhere. (one CDMI server at the plugfest was running on a Mac laptop).

Plugfest participants

There were a number people from both big and small organizations at SNIA’s plugfest.

Mark Carlson from Oracle was there and seemed to be leading the activity. He said I was free to attend but couldn’t say anything about what was and wasn’t working.  Didn’t have the heart to tell him, I couldn’t tell what was working or not from my limited time there. But everything seemed to be working just fine.

Carlson said that SNIA’s CDMI reference implementations had been downloaded 164 times with the majority of the downloads coming from China, USA, and India in that order. But he said there were people in just about every geo looking at it.  He also said this was the first annual CDMI plugfest although they had CDMI v0.8 running at other shows (i.e, SNIA SDC) before.

David Slik, from NetApp’s Vancouver Technology Center was there showing off his demo CDMI Ajax client and laptop CDMI server.  He was able to use the Ajax client to access all the CDMI capabilities of the cloud data object he was presenting and displayed the binary contents of an object.  Then he showed me the exact same data object (file) could be easily accessed by just typing in the proper URL into any browser, it turned out the binary was a GIF file.

The other thing that Slik showed me was a display of a cloud data object which was created via a “Cron job” referencing to a satellite image website and depositing the data directly into cloud storage, entirely at the server level.  Slik said that CDMI also specifies a cloud storage to cloud storage protocol which could be used to move cloud data from one cloud storage provider to another without having to retrieve the data back to the user.  Such a capability would be ideal to export user data from one cloud provider and import the data to another cloud storage provider using their high speed backbone rather than having to transmit the data to and from the user’s client.

Slik was also instrumental in the SNIA XAM interface standards for archive storage.  He said that CDMI is much more light weight than XAM, as there is no requirement for a runtime library whatsoever and only depends on HTTP standards as the underlying protocol.  From his viewpoint CDMI is almost XAM 2.0.

Gary Mazzaferro from AlloyCloud was talking like CDMI would eventually take over not just cloud storage management but also local data management as well.  He called the CDMI as a strategic standard that could potentially be implemented in OSs, hypervisors and even embedded systems to provide a standardized interface for all data management – cloud or local storage.  When I asked what happens in this future with SMI-S he said they would co-exist as independent but cooperative management schemes for local storage.

Not sure how far this goes.  I asked if he envisioned a bootable CDMI driver? He said yes, a BIOS CDMI driver is something that will come once CDMI is more widely adopted.

Other people I talked with at the plugfest consider CDMI as the new web file services protocol akin to NFS as the LAN file services protocol.  In comparison, they see Amazon S3 as similar to CIFS (SMB1 & SMB2) in that it’s a proprietary cloud storage protocol but will also be widely adopted and available.

There were a few people from startups at the plugfest, working on various client and server implementations.  Not sure they wanted to be identified nor for me to mention what they were working on. Suffice it to say the potential for CDMI is pretty hot at the moment as is cloud storage in general.

But what about cloud data consistency?

I had to ask about how the CDMI standard deals with eventual consistency – it doesn’t.  The crowd chimed in, relaxed consistency is inherent in any distributed service.  You really have three characteristics Consistency, Availability and Partitionability (CAP) for any distributed service.  You can elect to have any two of these, but must give up the third.  Sort of like the Hiesenberg uncertainty principal applied to data.

They all said that consistency is mainly a CDMI client issue outside the purview of the standard, associated with server SLAs, replication characteristics and other data attributes.   As such, CDMI does not define any specification for eventual consistency.

Although, Slik said that the standard does guarantee if you modify an object and then request a copy of it from the same location during the same internet session, that it be the one you last modified.  Seems like long odds in my experience.   Unclear how CDMI, with relaxed consistency can ever take the place of primary storage in the data center but maybe it’s not intended to.


Nonetheless, what I saw was impressive, cloud storage from multiple vendors all being accessed from the same client, using the same protocols.  And if that wasn’t simple enough for you, just use your browser.

If CDMI can become popular it certainly has the potential to be the new web file system.