Category Archives: compression

FDT – Deduplication Reimagined in OpenZFS

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Deduplication in OpenZFS has been a bugbear for some years now. As data sets get larger, they have become even more difficult in using the present DeDuplication Table (DDT) method. Deduplication in OpenZFS is often derided as overwhelming and sluggish in performance.

Moreover, there is a common folklore passed on and on about allocating 5GB of RAM for every 1TB to dedupe in OpenZFS. I don’t know where this “sizing” came about. Probably derived from something Jeff Bonwick wrote back in the early days of ZFS. But there is some truth to this “rule of thumb”, commonly passed around in the TrueNAS® circles.

Nevertheless, given the exponential growth of data, and the advancement of processing power in modern day computer systems, the OpenZFS development community has decided to revamp the DDT method. Several prominent luminaries from iXsystems™, Klara Systems and the OpenZFS community have got together in mid-2023 to develop FDT or Fast Dedupe Table. And we got to see FDT announced to the world in the most recent OpenZFS Developer Summit in November 2023.

Fast Dedupe Table (FDT)

Fast Dedupe Table (FDT) is a log-based dedupe. In OpenZFS, all the write block I/Os that come into OpenZFS are coalesced into transaction groups (TXGs), hashed and checksummed, before they are committed to persistent media.

The new implementation in FDT is to put these incoming TXGs checksums and hashes into an append-only log structure in persistent storage, and also tracking the hashed changes in an AVL-tree residing in the memory. An AVL tree is a self-balancing binary search tree structure that is very efficient in searching, thus giving FDT the speed in initiating the deduplication lookups and updates.

OpenZFS Fast Dedupe Table (FDT) in a nutshell

The append-only log structure works hand-in-hand with the AVL tree to accept and stage (including intelligent sorting) the hash entries that are coming in after the TXGs writes. Then at a certain marker, that could be at a particular time-based trigger or a high-water mark, then the entries in the logs and AVL tree are flushed to the ZAP (ZFS Attribute Processor) where the actual full map of the OpenZFS blocks reside.

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Backup – Lest we forget

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World Backup Day – March 31st

Last week was World Backup Day. It is on March 31st every year so that you don’t lose your data and become an April’s Fool the next day.

Amidst the growing awareness of the importance of backup, no thanks to the ever growing destructive nature of ransomware, it is important to look into other aspects of data protection – both a data backup/recovery and a data security –  point of view as well.

3-2-1 Rule, A-B-C and Air Gaps

I highlighted the basic 3-2-1 rule before. This must always be paired with a set of practised processes and policies to cultivate all stakeholders (aka the people) in the organization to understand the importance of protecting the data and ensuring data recoverability.

The A-B-C is to look at the production dataset and decide if the data should be stored in the Tier 1 storage. In most cases, the data becomes less active and these datasets may be good candidates to be archived. Once archived, the production dataset is smaller and data backup operations become lighter, faster and have positive causation as well.

Air gaps have returned to prominence since the heightened threats on data in recent years. The threats have pushed organizations to consider doing data offsite and offline with air gaps. Cost considerations and speed of recovery can be of concerns, and logical air gaps are also gaining style as an acceptable extra layer of data. protection.

Backup is not total Data Protection cyberdefence

If we view data protection more holistically and comprehensively, backup (and recovery) is not the total data protection solution. We must ignore the fancy rhetorics of the technology marketers that backup is the solution to ensure data protection because there is much more than that.

The well respected NIST (National Institute of Standards and Technology) Cybersecurity Framework places Recovery (along with backup) as the last pillar of its framework.

NIST Cybersecurity Framework

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Nakivo Backup Replication architecture and installation on TrueNAS – Part 1

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Backup and Replication software have received strong mandates in organizations with enterprise mindsets and vision. But lower down the rung, small medium organizations are less invested in backup and replication software. These organizations know full well that they must backup, replicate and protect their servers, physical and virtual, and also new workloads in the clouds, given the threat of security breaches and ransomware is looming larger and larger all the time. But many are often put off by the cost of implementing and deploying a Backup and Replication software.

So I explored one of the lesser known backup and recovery software called Nakivo® Backup and Replication (NBR) and took the opportunity to build a backup and replication appliance in my homelab with TrueNAS®. My objective was to create a cost effective option for small medium organizations to enjoy enterprise-grade protection and recovery without the hefty price tag.

This blog, Part 1, writes about the architecture overview of Nakivo® and the installation of the NBR software in TrueNAS® to bake in and create the concept of a backup and replication appliance. Part 2, in a future blog post, will cover the administrative and operations usage of NBR.

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Computational Storage embodies Data Velocity and Locality

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I have been earnestly observing the growth of Computational Storage for a number of years now.  It was known by several previous names, with the name “in-situ data processing” stuck with me the most. The Computational Storage nomenclature became more cohesive when SNIA® put together the CMSI (Compute Memory Storage Initiative) some time back. This initiative is where several standards bodies, the major technology players and several SIGs (special interest groups) in SNIA® collaborated to advance Computational Storage segment in the storage technology industry we know of today.

The use cases for Computational Storage are burgeoning, and the functional implementations of Computational Storage are becoming vital to tackle the explosive data tsunami. In 2018 IDC, in its Worldwide Global Datasphere Forecast 2021-2025 report, predicted that the world will have 175 ZB (zettabytes) of data. That number, according to hearsay, has been revised to a heady figure of 250ZB, given the superlative rate data is being originated, spawned and more.

Computational Storage driving factors

If we take the Computer Science definition of in-situ processing, Computational Storage can be distilled as processing data where it resides. In a nutshell, “Bring Compute closer to Storage“. This means that there is a processing unit within the storage subsystem which does not require the host CPU to perform processing. In a very simplistic manner, a RAID card in a storage array can be considered a Computational Storage device because it performs the RAID functions instead of the host CPU. But this new generation of Computational Storage has much more prowess than just the RAID function in a RAID card.

There are many factors in Computational Storage that make a lot sense. Here are a few:

  1. Voluminous data inundate the centralized architecture of the cloud platforms and the enterprise systems today. Much of the data come from end point devices – mobile devices, sensors, IoT, point-of-sales, video cameras, et.al. Pre-processing the data at the origin data points can help filter the data, reduce the size to be processed centrally, and secure the data before they are ingested into the central data processing systems
  2. Real-time processing of the data at the moment the data is received gives the opportunity to create the Velocity of Data Analytics. Much of the data do not need to move to a central data processing system for analysis. Often in use cases like autonomous vehicles, fraud detection, recommendation systems, disaster alerts etc require near instantaneous responses. Performing early data analytics at the data origin point has tremendous advantages.
  3. Moore’s Law is waning. The CPU (central processing unit) is no longer the center of the universe. We are beginning to see CPU offloading technologies to augment the CPU’s duties such as compression, encryption, transcoding and more. SmartNICs, DPUs (data processing units), VPUs (visual processing units), GPUs (graphics processing units), etc have come forth to formulate a new computing paradigm.
  4. Freeing up central resources with Computational Storage also accelerates the overall distributed data processing in the whole data architecture. The CPU and the adjoining memory subsystem are less required to perform context switching caused by I/O interrupts as in most of the compute/storage architecture today. The total effect relieves the CPU and giving back more CPU cycles to perform higher processing tasks, resulting in faster performance overall.
  5. The rise of memory interconnects is enabling a more distributed computing fabric of data processing subsystems. The rising CXL (Compute Express Link™) interconnect protocol, especially after the Gen-Z annex, has emerged a force to be reckoned with. This rise of memory interconnects will likely strengthen the testimony of Computational Storage in the fast approaching future.

Computational Storage Deployment Models

SNIA Computational Storage Universe in 2019

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How well do you know your data and the storage platform that processes the data

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Last week was consumed by many conversations on this topic. I was quite jaded, really. Unfortunately many still take a very simplistic view of all the storage technology, or should I say over-marketing of the storage technology. So much so that the end users make incredible assumptions of the benefits of a storage array or software defined storage platform or even cloud storage. And too often caveats of turning on a feature and tuning a configuration to the max are discarded or neglected. Regards for good storage and data management best practices? What’s that?

I share some of my thoughts handling conversations like these and try to set the right expectations rather than overhype a feature or a function in the data storage services.

Complex data networks and the storage services that serve it

I/O Characteristics

Applications and workloads (A&W) read and write from the data storage services platforms. These could be local DAS (direct access storage), network storage arrays in SAN and NAS, and now objects, or from cloud storage services. Regardless of structured or unstructured data, different A&Ws have different behavioural I/O patterns in accessing data from storage. Therefore storage has to be configured at best to match these patterns, so that it can perform optimally for these A&Ws. Without going into deep details, here are a few to think about:

  • Random and Sequential patterns
  • Block sizes of these A&Ws ranging from typically 4K to 1024K.
  • Causal effects of synchronous and asynchronous I/Os to and from the storage

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What happened to NDMP?

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The acronym NDMP shows up once in a while in NAS (Network Attached Storage) upgrade tenders. And for the less informed, NDMP (Network Data Management Protocol) was one of the early NAS data management (more like data mover specifications) initiatives to backup NAS devices, especially the NAS appliances that run proprietary operating systems code.

NDMP Logo

Backup software vendors often have agents developed specifically for an operating system or an operating environment. But back in the mid-1990s, 2000s, the internal file structures of these proprietary vendors were less exposed, making it harder for backup vendors to develop agents for them. Furthermore, there was a need to simplify the data movements of NAS files between backup servers and the NAS as a client, to the media servers and eventually to the tape or disk targets. The dominant network at the time ran at 100Mbits/sec.

To overcome this, Network Appliance® and PDC Solutions/Legato® developed the NDMP protocol, allowing proprietary NAS devices to run a standardized client-server architecture with the NDMP server daemon in the NAS and the backup service running as an NDMP client. Here is a simplified look at the NDMP architecture.

NDMP Client-Server Architecture

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Storage IO straight to GPU

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The parallel processing power of the GPU (Graphics Processing Unit) cannot be denied. One year ago, nVidia® overtook Intel® in market capitalization. And today, they have doubled their market cap lead over Intel®,  [as of July 2, 2021] USD$510.53 billion vs USD$229.19 billion.

Thus it is not surprising that storage architectures are changing from the CPU-centric paradigm to take advantage of the burgeoning prowess of the GPU. And 2 announcements in the storage news in recent weeks have caught my attention – Windows 11 DirectStorage API and nVidia® Magnum IO GPUDirect® Storage.

nVidia GPU

Exciting the gamers

The Windows DirectStorage API feature is only available in Windows 11. It was announced as part of the Xbox® Velocity Architecture last year to take advantage of the high I/O capability of modern day NVMe SSDs. DirectStorage-enabled applications and games have several technologies such as D3D Direct3D decompression/compression algorithm designed for the GPU, and SFS Sampler Feedback Streaming that uses the previous rendered frame results to decide which higher resolution texture frames to be loaded into memory of the GPU and rendered for the real-time gaming experience.

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First looks into Interplanetary File System

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The cryptocurrency craze has elevated another strong candidate in recent months. Filecoin, is leading the voice of a decentralized Internet, the next generation Web 3.0. In this blog, I am not going to write much about the Filecoin frenzy but the underlying distributed file system that powers this phenomenon – The Interplanetary File System.

[ Note: This is still a very new area for me, and the rest of the content of this blog is still nascent and developing ]

Interplanetary File System

Tremulous Client-Server web architecture

The entire Internet architecture is almost client and server. Your clients like browsers, apps, connect to Web services served from a collection of servers. As Web 3.0 approaches (some say it is already here), the client-server model is no longer perceived as the Internet architecture of choice. Billions, and billions of users, applications, devices relying solely on a centralized service would lead to many impactful consequences, and the reasons for decentralization, away from the client-server architecture models of the Internet are cogent.

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A FreeNAS Compression Tale

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David vs Goliath Credit: Miguel Robledo of https://www.artstation.com/miguel_robledo

David vs Goliath

It was an underdog tale worthy of the biblical book of Samuel. When I first caught wind of how FreeNAS™ compression prowess was going against NetApp® compression and deduplication in one use case, I had to find out more. And the results in this use case was quite impressive considering that FreeNAS™ (now known as TrueNAS® CORE) is the free, open source storage operating system and NetApp® Data ONTAP, is the industry leading, enterprise, “king of the hill” storage data management software.

Certainly a David vs Goliath story.

Compression in FreeNAS

Ah, Compression! That technology that is often hidden, hardly seen and often forgotten.

Compression is a feature within FreeNAS™ that seldom gets the attention. It works, and certainly is a mature form of data footprint reduction (DFR) technology, along with data deduplication. It is switched on by default, and is the setting when creating a dataset, as shown below:

Dataset creation with Compression (lz4) turned on

The default compression algorithm is lz4 which is fast but poor in compression ratio compared to gzip and bzip2. However, lz4 uses less CPU cycles to perform its compression and decompression processing, and thus the impact on FreeNAS™ and TrueNAS® is very low.

NetApp® ONTAP, if I am not wrong, uses lzopro as default – a commercial and optimized version of the open source LZO compression library. In addition, NetApp also has their data deduplication technology as well, something OpenZFS has to improve upon in the future.

The DFR report

This brings us to the use case at one of iXsystems™ customers in Taiwan. The data to be reduced are mostly log files at the end user, and the version of FreeNAS™ is 11.2u7. There are, of course, many factors that affect the data reduction ratio, but in this case of 4 scenarios,  the end user has been running this in production for over 2 months. The results:

FreeNAS vs NetApp Data Footprint Reduction

In 2 of the 4 scenarios, FreeNAS™ performed admirably with just the default lz4 compression alone, compared to NetApp® which was running both their inline compression and deduplication.

The intention to post this report is not to show that FreeNAS™ is better in every case. It won’t be, and there are superior data footprint reduction tech out there which can outperform it. But I would expect potential and existing end users to leverage on the compression capability of FreeNAS™ which is getting better all the time.

A better compression algorithm

Followers of OpenZFS are aware of the changing of times with OpenZFS version 2.0. One exciting update is the introduction of the zstd compression algorithm into OpenZFS late last year, and is already in TrueNAS® CORE and Enterprise version 12.x.

What is zstd? zstd is a fast compression algorithm that aims to be as efficient (or better) than gzip, but with better speed closer to lz4, relatively. For a long time, the gzip compression algorithm, from levels 1-9, has been serving very good compression ratio compared to many compression algorithms, lz4 included.

However, the efficiency came at a higher processing price and thus took a longer time. At the other end, lz4 is fast and lightweight, but its reduction ratio efficiency is very poor. zstd intends to be the in-between of gzip and lz4. In the latest results published by Facebook’s github page,

zstd performance benchmark against other compression algorithms

For comparison, zstd (level -1) performed very well against zlib, the data compression library in gzip. It was made known there are 22 levels of compression in zstd but I do not know how many levels are accepted in the OpenZFS development.

At the same time, compression takes advantage of multi-core processing, and actually can speed up disk I/O response because the original dataset to be processed is smaller after the compression reduction.

While TrueNAS® still defaults lz4 compression as of now, you can probably change the default compression with a command

# zfs set compression=zstd-6 pool/dataset

Your choice

TrueNAS® and FreeNAS™ support multiple compression algorithms. lz4, gzip and now zstd. That gives the administrator a choice to assign the right compression algorithm based on processing power, storage savings, and time to get the best out of the data stored in the datasets.

As far as the David vs Goliath tale goes, this real life use case was indeed a good one to share.

 

Falconstor Software Defined Data Preservation for the Next Generation

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Falconstor® Software is gaining momentum. Given its arduous climb back to the fore, it is beginning to soar again.

Tape technology and Digital Data Preservation

I mentioned that long term digital data preservation is a segment within the data lifecycle which has merits and prominence. SNIA® has proved that this is a strong growing market segment through its 2007 and 2017 “100 Year Archive” surveys, respectively. 3 critical challenges of this long, long-term digital data preservation is to keep the archives

  • Accessible
  • Undamaged
  • Usable

For the longest time, tape technology has been the king of the hill for digital data preservation. The technology is cheap, mature, and many enterprises has built their long term strategy around it. And the pulse in the tape technology market is still very healthy.

The challenges of tape remain. Every 5 years or so, companies have to consider moving the data on the existing tape technology to the next generation. It is widely known that LTO can read tapes of the previous 2 generations, and write to it a generation before. The tape transcription process of migrating digital data for the sake of data preservation is bad because it affects the structural integrity and quality of the content of the data.

In my times covering the Oil & Gas subsurface data management, I have seen NOCs (national oil companies) with 500,000 tapes of all generations, from 1/2″ to DDS, DAT to SDLT, 3590 to LTO 1-7. And millions are spent to transcribe these tapes every few years and we have folks like Katalyst DM, Troika and more hovering this landscape for their fill.

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