Category Archives: Data Corruption

Crash consistent data recovery for ZFS volumes

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While TrueNAS® CORE and TrueNAS® Enterprise are more well known for its NAS (network attached storage) prowess, many organizations are also confidently placing their enterprise applications such as hypervisors and databases on TrueNAS® via SANs (storage area networks) as well. Both iSCSI and Fibre Channel™ (selected TrueNAS® Enterprise storage models) protocols are supported well.

To reliably protect these block-based applications via the SAN protocols, ZFS snapshot is the key technology that can be dependent upon to restore the enterprise applications quickly. However, there are still some confusions when it comes to the state of recovery from the ZFS snapshots. On that matter, this situations are not unique to the ZFS environments because as with many other storage technologies, the confusion often stem from the (mis)understanding of the consistency state of the data in the backups and in the snapshots.

Crash Consistency vs Application Consistency

To dispel this misunderstanding, we must first begin with the understanding of a generic filesystem agnostic snapshot. It is a point-in-time copy, just like a data copy on the tape or in the disks or in the cloud backup. It is a complete image of the data and the state of the data at the storage layer at the time the storage snapshot was taken. This means that the data and metadata in this snapshot copy/version has a consistent state at that point in time. This state is frozen for this particular snapshot version, and therefore it is often labeled as “crash consistent“.

In the event of a subsystem (application, compute, storage, rack, site, etc) failure or a power loss, data recovery can be initiated using the last known “crash consistent” state, i.e. restoring from the last good backup or snapshot copy. Depending on applications, operating systems, hypervisors, filesystems and the subsystems (journals, transaction logs, protocol resiliency primitives etc) that are aligned with them, some workloads will just continue from where it stopped. It may already have some recovery mechanisms or these workloads can accept data loss without data corruption and inconsistencies.

Some applications, especially databases, are more sensitive to data and state consistencies. That is because of how these applications are designed. Take for instance, the Oracle® database. When an Oracle® database instance is online, there is an SGA (system global area) which handles all the running mechanics of the database. SGA exists in the memory of the compute along with transaction logs, tablespaces, and open files that represent the Oracle® database instance. From time to time, often measured in seconds, the state of the Oracle® instance and the data it is processing have to be synched to non-volatile, persistent storage. This commit is important to ensure the integrity of the data at all times.

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The Starbucks model for Storage-as-a-Service

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Starbucks™ is not a coffee shop. It purveys beyond coffee and tea, and food and puts together the yuppie beverages experience. The intention is to get the customers to stay as long as they can, and keep purchasing the Starbucks’ smorgasbord of high margin provisions in volume. Wifi, ambience, status, coffee or tea with your name on it (plenty of jokes and meme there), energetic baristas and servers, fancy coffee roasts and beans et. al. All part of the Starbucks™-as-a-Service pleasurable affair that intends to lock the customer in and have them keep coming back.

The Starbucks experience

Data is heavy and they know it

Unlike compute and network infrastructures, storage infrastructures holds data persistently and permanently. Data has to land on a piece of storage medium. Coupled that with the fact that data is heavy, forever growing and data has gravity, you have a perfect recipe for lock-in. All storage purveyors, whether they are on-premises data center enterprise storage or public cloud storage, and in between, there are many, many methods to keep the data chained to a storage technology or a storage service for a long time. The storage-as-a-service is like tying the cow to the stake and keeps on milking it. This business model is very sticky. This stickiness is also a lock-in mechanism.

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What If – The other side of Storage FUDs

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Streaming on Disney+ now is Marvel Studios’ What If…? animated TV series. In the first episode, Peggy Carter, instead of Steve Rogers, took the super soldier serum and became the first Avenger. The TV series explores alternatives and possibilities of what we may have considered as precept and the order of things.

As storage practitioners, we are often faced with certain “dogmatic” arguments which were often a mix of measured actuality and marketing magic – aka FUD (fear, uncertainty, doubt). Time and again, we are thrown a curve ball, like “Oh, your competitor can do this. Can you?” Suddenly you are feeling pinned to a corner, and the pressure to defend your turf rises. You fumbled; You have no answer; Game over!

I experienced these hearty objections many times over. The best experience was one particular meeting I had during my early days with NetApp® in 2000. I was only 1-2 months with the company, still wet between the ears with the technology. I was pitching the SnapMirror® to Ericsson Malaysia when the Scandinavian manager said, “I think you are lying!“. I was lost without a response. I fumbled spectacularly although I couldn’t remember if we won or lost that opportunity.

Here are a few I often encountered. Let’s play the game of What If …?

What If …?

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Rethinking File Security Fundamentals

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I took a week off blogging last week but the lazy days were inundated by bad news. A few more devastating ransomware attacks. This time, Colonial Pipeline in the US was hacked and its networks were shutdown by ransomware. These ransomware threats are never ending, and they are getting more damaging than ever. It is like trying to plug a leaking boat with your hands, and more leaks appear as you plug them.

More ransomware news hitting healthcare around the world last week:

We are forever chasing for a solution, forever losing because almost all technology defenses to protect the data against ransomware are reactive. Why is ransomware still such a big threat then?  Time to rethink file security fundamentals.

Data everywhere

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The other pandemic – Datanemic

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It is a disaster. No matter what we do, the leaks and the cracks are appearing faster than we are fixing it. It is a global pandemic.

I am not talking about COVID-19, the pandemic that has affected our lives and livelihood for over a year. I am talking about the other pandemic – the compromise of security of data.

In the past 6 months, the data leaks, the security hacks, the ransomware scourge have been more devastating than ever. Here are a few big ones that happened on a global scale:

Data Security Breach, Cyber Attack, Ransomware

Closer to home, here in South East Asia, we have

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Trusting your storage – It’s not about performance

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I have taken some downtime from my blog since late October. Part of my “hiatus” was my illness which had affected my right kidney but I am happy to announce that I am well again. During this period, I spent a lot of the time reading the loads of storage technologies announcements and their marketing calls and almost every single one of them touts Performance as if it is the single “sellable” feature of the respective storage vendor. None ever positions data integrity and the technology behind it in what I believe as the most important and most fundamental feature of any storage technology – Reading the right data exactly it was written into the storage array.

[ Note: Data integrity is even more critical in cloud storage and data corruption, especially the silent ones are even more acute in the clouds ]

Sure, this fundamental feature sounds like it is a given thing in any storage array but believe me, there are enterprise storage arrays which have failed to deliver this simple feature properly. I have end users coming to me through out my storage career that they have database corruption, or file corruption and unable to access their data in an acceptable manner. Data corruption is real folks!

Data corruption.

After several weeks of reading these stuff, I got jaded with so many storage vendors playing leapfrog announcements with their millions of IOPS boasts.

The 3 legged stool

Rewind to circa 2012, just about the time when EMC® acquired XtremIO™. XtremIO™ was a nascent All-Flash startup, and many, including yours truly, really saw the EMC® acquisition was about a high performant storage array. I was having an email conversation with Shahar Frank, one of the co-founders of XtremIO™, and expressing my views about their performance. What Shahar replied surprised me.

The fundamentals of the strength of a storage array was a like a 3-legged stool. 2 legs of the stool would be Performance, and Protection, but with 2 legs, the person sitting on the stool would fall. The 3rd leg would stabilize the balance of the stool, and this 3rd leg was Reliability. This stumped me because XtremIO™’s most sellable feature was Performance. But the wisdom of Shahar pointed to Reliability, the least exciting feature and the most dull of the 3. He was brilliant, of course and went on to found ElastiFile (acquired by Google™), but that’s another story for another day.

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Valuing the security value of NAS storage

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Garmin paid, reportedly millions. Do you sleep well at night knowing that the scourge of ransomware is rampant and ever threatening your business. Is your storage safe enough or have you invested in a storage which was the economical (also to be known as cheap) to your pocket?

Garmin was hacked by ransomware

I have highlighted this before. NAS (Network Attached Storage) has become the goldmine for ransomware. And in the mire of this COVID-19 pandemic, the lackadaisical attitude of securing the NAS storage remains. Too often than not, end users and customers, especially in the small medium enterprises segment, continue to search for the most economical NAS storage to use in their business.

Is price the only factor?

Why do customers and end users like to look at the price? Is an economical capital outlay of a cheap NAS storage with 3-year hardware and shallow technical support that significant to appease the pocket gods? Some end users might decided to rent cloud file storage, Hotel California style until they counted the 3-year “rental” price.

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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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The Falcon to soar again

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One of the historical feats which had me mesmerized for a long time was the 14-year journey China’s imperial treasures took to escape the Japanese invasion in the early 1930s, sandwiched between rebellions and civil wars in China. More than 20,000 pieces of the imperial treasures took a perilous journey to the west and back again. Divided into 3 routes over a decade and four years, not a single piece of treasure was broken or lost. All in the name of preservation.

Today, that 20,000 over pieces live in perpetuity in 2 palaces – Beijing Palace Museum in China and National Palace Museum Taipei in Taiwan

Digital data preservation

Digital data preservation is on another end of the data lifecycle spectrum. More often than not, it is not the part that many pay attention to. In the past 2 decades, digital data has grown so much that it is now paramount to keep the data forever. Mind you, this is not the data hoarding kind but to preserve the knowledge and wisdom which is in the digital content of the data.

[ Note: If you are interested to know more about Data -> Information -> Knowledge -> Wisdom, check out my 2015 article on LinkedIn ]

SNIA (Storage Networking Industry Association) conducted 2 surveys – one in 2007 and another in 2017 – called the 100 Year Archive, and found that the requirement for preserving digital data has grown multiple folds over the 10 years. In the end, the final goal is to ensure that the perpetual digital contents are

  • Accessible
  • Undamaged
  • Usable

All at an affordable cost. Therefore, SNIA has the vision that the digital content must transcend beyond the storage medium, the storage system and the technology that holds it.

The Falcon reemerges

A few weeks ago, I had the privilege to speak with Falconstor® Software‘s David Morris (VP of Global Product Strategy & Marketing) and Mark Delsman (CTO). It was my first engagement with Falconstor® in almost 9 years! I wrote a piece of Falconstor® in my blog in 2011.

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btrfs butter gone bad?

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I wrote about btrfs 8 years ago.

Since then, it has made its way into several small to mid-end storage solutions (more NAS inclined solutions) including Rockstor, Synology, Terramaster, and Asustor. In the Linux world, SUSE® Linux Enterprise Server and OpenSUSE® use btrfs as the default OS file system. I have decided to revisit btrfs filesystem to give some thoughts about its future.

Have you looked under the hood?

The sad part is not many people look under the hood anymore, especially for the market the btrfs storage vendors are targeting. The small medium businesses just want a storage which is cheap. But cheap comes at a risk where the storage reliability and data integrity are often overlooked.

The technical conversation is secondary and thus the lack of queries for strong enterprise features may be leading btrfs to be complacent in its development.

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