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Comment by georgewfraser | Hacker News Reader

I am truly baffled by the desire to build new data lakes. I understand why Hadoop data lakes came to be: Teradata charged a lot for storage. But now there are database systems that use object storage under-the-hood: Snowflake, BigQuery, Redshift RA3, Databricks Delta Lake. They give you the same low cost of object storage, but with a nice high-level relational interface. I am mystified by why someone would want to build their own data lake rather than just use one of these systems.

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All the tools you mention are great for their specific use cases, e.g. Snowflake BigQuery and RedShift are great for analytics over big data, the very common COUNT/SUM/AVG/PARTITION/GROUP BY analysis. But as with any other tool, they're not a good/perfect fit for diverse analysis methods of diverse data types, which I think is what a data lake aims at. Analyzing a large JSON dataset on Snowflake is possible, but either too slow or expensive when compared with more appropriate tools (e.g. Elasticsearch or a Python notebook running PySpark).

Having a data lake - which I understand as a repository of raw data of diverse types, regardless of the tools - structured in a tool like S3 is very useful when you have multiple use cases over data of different kinds.

For example, you could store audio files from customer calls and have them processed automatically by Spark jobs (e.g. for transcript and stats generation), structure and store call stats on a database for analytics, and do further analysis via notebooks on data science initiatives (e.g. sentiment analysis). This is akin to having a staging area for complex and diverse data types, and S3 is useful for this because of its speed, scale and management features.

Teradata or Snowflake aren't a great fit for use cases like these, but they are great if the use case is to get answers to questions like "top 3 operators per team in volume of calls, by department and region, in last quarter" if the volume of calls is big.

If I understood correctly, I think your comment was more focused on why use new tools when the existing are mature, but I think big data tools have had to become more specialized and targeted for specific use cases. But if the question is "why build more than one data lake", the only reason I can see is organizational: teams or different areas of an organization either need their own data lake because they have specific needs (which is rare) or won't/can't collaborate with others to have a shared asset.

I agree that no matter what you're going to store unstructured binary data, like audio files, in object storage. But that is perfectly compatible with storing structured data in a relational database.

> they are great if the use case is to get answers to questions like "top 3 operators per team in volume of calls..."

You are straw-manning Snowflake/BQ. Just because they are SQL database systems doesn't mean you have to do 100% of your analysis in SQL. You can use other systems, like Spark, PyTorch, Tensorflow, to work with data that you manage inside a RDBMS. There are some issues with bandwidth getting data between systems, but these issues are getting solved (by Arrow!) and in the meantime unload-to/load-from S3 is a good workaround.

I've heard a lot of people make these same arguments and I've tentatively concluded it's mostly motivated reasoning. Engineers like to engineer things. They start by trying to make the obvious, boring system work, but when they run into an obstacle they immediately jump to "I need to build a new system using $TECHNOLOGY."

Snowflake and BigQuery are quite expensive for big datasets.

Databricks Delta Lake has some use cases, but there are some aspects that are rough around the edges. vacuuming is very slow, the design decision to store partitioned data on disk in folders has certain pros / cons, etc.

There are a lot of great products in the data lake space, but lots more innovation is needed going forward.

> Snowflake and BigQuery are quite expensive for big datasets.

This is just flatly untrue---they are nearly the same cost/TB as object storage, and they store everything in compressed columnarized format, so they're about as efficient as you can get.

I have heard many people make the same claim. I can't figure it out. Is there something wrong with my calculator???

The storage costs are only a tiny fraction of the costs involved with accessing and analyzing the data using snowflake "credits"

For sure, but you're not going to fix that by making your own data lake using, for example, Parquet-on-S3. You're still going to pay the cost of compute when you analyze that data, and a well-optimized commercial database system is extremely hard to beat. Even if you look at Presto, and you exclude the people costs of managing it yourself, it still can't beat the commercial systems: https://fivetran.com/blog/warehouse-benchmark

That's because Snowflake happens to charge relatively little for backing storage at the moment. As I recall it's about the same as object storage. Virtual data warehouses on the other hand are quite expensive, especially if they have a lot of compute.

Surely those are all tools for building a data lake, and the stack described in the article is just another tool for doing the same? It's a reasonable architectural choice...

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