Primary and Secondary Storage aka Tiering in 2017


History of Hierarchical Storage Management

Having multiple storage tiers is not a new thing. Actually history of hierarchical storage management (HSM) goes quite far. It was actually first implemented by IBM on their mainframe computer platforms to reduce to the cost of data storage, and to simplify the process to get data from slower media. Idea was to that the actual user would not need to know where the data was actually stored and how to get it back – with HSM the computer would retrieve the asked data automatically.

Historically HSM was somewhat buried when world went from 1st platform to 2nd platform (Client-Server, PC-era). Quite soon many organizations realised they still had application needs for centralized storage platforms and so the storage area networks (SAN) was pretty much born. After server virtualization exploded need for high performance storage organizations realized that, again, it was too expensive to run all application data in one high performance storage tier or it was just too difficult to move data between isolated storage tiers. Tiering, or HSM, was actually born again.

Many storage vendors implemented somekind of tiering system. Some implemented system monitoring actual hot blocks and then migrated those hot blocks between slower and faster tier or 3-tier (SSD, SAS and SATA). Comparing these systems only difference was typically size of the block moved and frequency of moving blocks. This was approach for IBM, EMC and HDS (and many others also), just few to name. There was no big problem with this approach since it solved many problems but in many cases it just reacted too slow to performance needs. With proper design this works very well.

Other vendors implemented tiering based on caching. Every storage system has cache (read and write) but these vendors approach for tiering was implementing method to add high performance disks (SSD) to extend size of the cache. This reacts very fast to changes and typically doesn’t need any tuning. However this approach doesn’t allow you to pin application data to selected tier so proper design is critical.

All flash storage changed the game


Late 2000 all flash storage systems moved very high performance applications from tiered storage to pure flash platform. Price of the flash was very high and typically you had one all flash system per application. Few years later all flash systems actually replaced spinning disks and tiered storage pretty much on most of the organizations since pricing of the flash became affordable and implementation of efficiency technologies (deduplication and compression) meant you could put more data on same disk capacity which actually dropped the gigabyte pricing quite close to high performance spinning disks (10/15k SAS drives).

Suddenly you didn’t need any tiering since all flash systems gave you enough performance to run all your applications but this introduced isolated silos and moving from 2nd platform to 3rd platform means very dramatical growth in data amounts.

Living in the world of constant data growth

Managing unstructured data continues to be a challenge for most of the organizations. When Enterprise Strategy Group surveys IT managers about their biggest overall storage challenges, growth and management of unstructured data comes out at or near the top of the list most of the time.

And that challenge isn’t going away. Data growth is accelerating, driven by a number of factors:

The Internet of Things

We now have to deal with sensor data generated by everything. Farmers are putting health sensors on livestock so they can detect issues early on, get treatment and stop illness from spreading. They’re putting sensors in their fields to understand how much fertilizer or water to use, and where. Everything from your refrigerator to your thermostat will be generating actionable data in the not too distant future.


Bigger, much richer files

Those super-slow motion videos we enjoy during sporting events are shot at 1,000 frames per second with 2 MB frames. That means 2 GB of capacity is required for every second of super-slow motion video captured. And it’s not all about media and entertainment; think about industry-specific use cases leveraging some type of imaging, such as healthcare, insurance, construction, gaming and anyone using video surveillance.

More data capture devices

More people are generating more data than ever before. The original Samsung Galaxy S smartphone had a 5 megapixel camera, so each image consumed 1.5 MB of space compressed (JPEG) or 15 MB raw. The latest Samsung smartphone takes 16 megapixel images, consuming 4.8 MB compressed/48 MB raw storage — thats a 3 fold increase in only few years.

Enterprise Data Lake is 2017 version of tiered storage

Tiered storage, as it used to be implemented, has born again with next generation of old idea. In modern world tiering is solving problems related to massive data growth. More and more production data is going to All Flash arrays but since only 10-30% of actual data is really hot organizations must implement somekind of secondary storage vision to be able move cold data from still expensive primary storage to much cheaper secondary storage.

The secondary storage today is object based storage to response fast pace of data growth and data locality problems of IoT. Organizations are going to use this same object storage platform for their Internet of Things needs and also maybe place to hold their production application data backups.


How to backup object storage?



Traditional file server may have outlived it’s usefulness for an increasing number of organizations in past years. Traditionally these file servers were designed in an era where typically all employees were sitting in one location and remote workers / road warriors were quite rare and even then only files they created were office documents (word, excel, powerpoint, etc). However time has changed and now it’s new normal that organizations have employees all over the globe and also IoT (Internet of Things) has changed landscape very much; they generate far more data than normal users ever will and this data must be kept in safe location since data is now the main asset of many organizations and normal file servers are not enough to meet the requirements of the modern data center anymore.

So we got an object storage to solve issues but first you need to understand what is an object storage and how it differs from traditional file servers.

So what is an object storage?

For years data was typically stored in a POSIX file system (or databases but let’s focus on file services here) where data is organized in volumes, folders/directories and sub-folders/sub-directories. Data written to file system contains two actual pieces; the data written to file system itself and also metadata which in POSIX file systems is typically simple and includes only information about creation date, change date, etc. However object storages work a bit differently.

Object storage is also used to store data but unlike POSIX file systems, an object storage system gives each object unique id, rather than name, which is managed in flat index instead of folders. In POSIX file systems applications access files based on directory and filenames but in object storage they access files (or objects here) by providing an unique object id to fetch/re-write information. Because of this flat architecture object storage provides much greater scalability and faster access to much higher quantity of files compared most traditional POSIX based file servers. Flat architecture enables also much richer medata information for actual data since most object storage systems allow much broader set of information stored  per object than traditional POSIX file system. You can store all the same information (creation date, change date, etc) but also add additional information like expiration dates, protection requirements, information for application what type of file is, what kind of information it contains etc.

So in general object storages are designed to handle an massive amount of data; it can be data stored in large objects like video/images/audio or very billions of very small objects containing IoT device information like sensor data. Typical object storage can scale to very big and this raises a question. How we can backup the data stored in object storages?

Why object storage is not that easy to backup?

Problems Ahead

Traditionally object storage solutions are considered when you have massive amounts of data like petabytes of data and/or billions of objects (files). This kind of platform challenges your traditional enterprise backup solution. Think about it while. If you need to backup all changed objects how long it will take for enterprise backup server to lookup which object has been changed and then fetch them from storage and put them on disk and/or tape. With large scale environments this slowly becomes just impossible. You need to implement other kind of solutions.

From backups to data protection

First step here is to change our minds from backups to data protection. Backup is just a method to protect your data, isn’t it? When we understand this we can start thinking how we can protect our data in object storage environments. There is always the traditional way to protect it, but let’s think how object storage environments are protected in real life.

Object Storage Systems tend to have ability to have versioning built in. What this is is just a method to save old version of object in case of change or delete. So even when user deletes objects they are not removed from system in real life but just marked as deleted. When we combine this to multisite solutions we actually have built in data protection solution capable to protect your valuable data. However we need to have also smart information lifecycle management in our object storage to be able to actually remove deleted objects when our ILM rules says so. Like after ‘deleting’ (marking object deleted) we would still keep last version for 5 years and after that we will remove it from system.

This kind of approach has one limitation you must keep in your mind what comes to data durability. What typical data protection systems do not protect against is bit rot – the concept of magnetic degradation over time. Magnetic storage degrades over time and this is not a matter if the data will be corrupted but rather it is when it will. The good thing here is that enterprise ready object storage solution should have methods to prevent this since should have methods to monitor and repair the affects of magnetic degradation with use of unique identifier for each object that is the result of some type of algorithm (e.g. SHA-256) being run against the contents of the object. By re-running the algorithm against an object and comparing it against its unique identifier, the software makes sure that no bit rot corrupts the file.

There is of course still one issue which must be solved different way – nasty admin. There is always possibility that storage admin of object storage solution just deletes whole system. But let’s think this in future post coming later this spring!