Boosting Solid States beyond SATA

Lately, I have been getting deeper and deeper into low-level implementation related to storage technologies. In my previous blog, I was writing my learning adventure with Priority Flow Control (PFC) and intend to further the Data Center Bridging concepts with future blog entries.

Before I left for Sydney for a holiday last week, I got sidetracked into exciting stuff that’s happening in my daily encounters with friends and new friends. 2 significant storage related technologies fell onto my lap. One is NVMe (Non-Volatile Memory express) and the other FPGA (Field Programmable Gate Array).

While this blog is going to be about NVMe, I actually found FPGA much more exciting to me. Through conversations, I found that there are 2 “biggies” in the FPGA world, and they are designed and manufactured by Xilink and Altera. I admit that I have not done my homework on FPGA yet, having just returned from Sydney last night. I will blog about FPGA in future blogs.

But NVMe is also an important technology direction to the storage world as well.

I think most of us are probably already mesmerized by solid state drives. The bombardment of marketing, presentations, advertising and whatever else the vendors do to promote (and self-promote) solid state drives are inundating the intellectual senses of consumers and enterprises alike. And yet, many vendors do not explain both the pros and cons of integrating solid states into their IT environment. Even worse, many don’t even know the strengths and weaknesses of solid states, hence creating some exaggeration that continues to create a spiral vortex of inaccuracies. Like a self-feeding frenzy, the industry seems to have placed solid state storage as the saviour of the enterprise storage world. Go figure with that!

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AoE – All about Ethernet!

This is long overdue.

A reader of my blog asked if I could do a piece on Coraid. Coraid who?

This name is probably a name not many people heard of in Malaysia. Even most the storage guys that I talk to never heard of it.

I have known about Coraid for a few years now (thanks to my incessant reading habits), looking at it from nonchalant point of view.  But when the reader asked about Coraid, I contacted Kevin Brown, CEO of Coraid, whom I am not exactly sure how I was connected through LinkedIn. Kevin was very responsive and got one of their Directors to contact me. Kaushik Shirhatti was his name and he was very passionate to share their Coraid technology with me. Thanks Kevin and Kaushik!

That was months ago but the thought of writing this blog post has been lingering. I had to scratch the itch. ;-)

So, what’s up with Coraid? I can tell that they are different but seems to me that their entire storage architecture is so simple that it takes a bit of time for even storage guys to wrap their head around it. Why do I say that?

For storage guys (like me), we are used to layers. One of the memorable movie quotes I recalled was from Shrek: “Orges are like onions! Onions have layers!“.

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The future is intelligent objects

We are used to block-based approach and also the file-based approach to data. The 2 diagrams below shows the basics of how we access data in both block-based and file-based data on the storage device.

 

For block-based , the storage of the blocks is merely in arrays of unrelated contiguous blocks. For file-based, as seen below,

 

there is another layer of abstraction, and this is called the file system. But if you seen both diagrams above, there are some random numbers in light blue and that is to represent the storage device, the hard disk drive’s export of “containers” to the file system or the application that is accessing the storage device. This is usually the LBA (Logical Block Addressing), which is basically set of schematics that defines the locations on the hard disk drives. LBA tells the location of where the data is stored. For more information about LBA, check out this Wikipedia definition. But the whole idea is LBA is dumb. It is pretty much static and exported to file systems and applications so that these guys can do something with it.

There’s something brewing in the background since 1994 and it is one of the many efforts to make intelligent storage devices. This new object-based interface was part of the research project done by Carnegie-Mellon University (CMU). Initially, it was known as Network Attached Secure Disk (NASD) but eventually made its way to the working group in SNIA, and developing it for ANSI T10 INCITS standard. ANSI T10 is the guardian of all SCSI standards. This is called Object Storage Device (OSD). The SCSI architecture diagram below shows the layer where OSD resides.

 

The motivation for this simple: To make storage devices of today to do more computational work, in particularly I/O, relieving the hosts and the local systems to concentrate other computational processing work. And the same time, the local systems must have some level of interactivity and management between the storage object and the computational hosts.

In the diagram below which compares both block-based and OSD,

 

you can see the separation of file system management interface that is at the kernel-space of the local host/system and this is replaced by the OSD Management interface at the storage device.

What does this all mean? This means that using LBA type of addressing that we are familiar with in the block-based and file-based storage is no longer the way to go, because as I mentioned before, LBA is dumb.

OSD, in some way, replaces the LBA with OIDs (Object IDs). The existing local system and/or its file system will interact with the storage devices with OIDs and the OIDs links to its respective objects storage. And the object will carry a lot of metadata, that represents the object, giving it the intelligent and management capability of the object.

 

 

The prominence of the metadata in the OSD would mean that we can build much more intelligent systems in the future. The OIDs and the objects can be grouped together in a flat design or can be organized and categorized in a virtual, hierarchical model.

 

Object storage is an intelligent evolution of disk drives that can store and serve objects rather than simply place data on tracks and sectors. And it can bring the following benefits:

  • Intelligent space management in the storage layer
  • Data aware pre-fetching and caching
  • Robust shared access by multiple clients
  • Scalable performance using off-loaded data path
  • Reliability security

Several vendors such as EMC and NetApp are already supporting OSD.