An official website of the United States government
With the ever-increasing dataset sizes, several file formats such as Parquet, ORC, and Avro have been developed to store data efficiently, save the network, and interconnect bandwidth at the price of additional CPU utilization. However, with the advent of networks supporting 25-100 Gb/s and storage devices delivering 1,000,000 reqs/sec, the CPU has become the bottleneck trying to keep up feeding data in and out of these fast devices. The result is that data access libraries executed on single clients are often CPU-bound and cannot utilize the scale-out benefits of distributed storage systems. One attractive solution to this problem is to offload data-reducing processing and filtering tasks to the storage layer. However, modifying legacy storage systems to support compute offloading is often tedious and requires an extensive understanding of the system internals. Previous approaches re-implemented functionality of data processing frameworks and access libraries for a particular storage system, a duplication of effort that might have to be repeated for different storage systems. This paper introduces a new design paradigm that allows extending programmable object storage systems to embed existing, widely used data processing frameworks and access libraries into the storage layer with no modifications. In this approach, data processing frameworks and access libraries can evolve independently from storage systems while leveraging distributed storage systems’ scale-out and availability properties. We present Skyhook, an example implementation of our design paradigm using Ceph, Apache Arrow, and Parquet. We provide a brief performance evaluation of Skyhook and discuss key results.
more »
« less
Scaling databases and file apis with programmable ceph object storage
The Skyhook Data Management project (SkyhookDM.com) at the Center for Research in Open Source Software (cross.ucsc.edu) at UC Santa Cruz implements customized extensions through Ceph's object class interface that enables offloading database operations to the storage system. In our previous Vault '19 talk, we showed how SkyhookDM can transparently scale out databases. The SkyhookDM Ceph extensions are an example of our 'programmable storage' research efforts at UCSC, and can be accessed through commonly available external/foreign table database interfaces. Utilizing fast in-memory serialization libraries such as Google Flatbuffers and Apache Arrow, SkyhookDM currently implements common database functions such as SELECT, PROJECT, AGGREGATE, and indexing inside Ceph, along with lower-level data manipulations such as transforming data from row to column formats on RADOS servers. In this talk, we will present three of our latest developments on the SkyhookDM project since Vault '19. First, SkyhookDM can be used to also offload operations of access libraries that support plugins for backends, such as HDF5 and its Virtual Object Layer. Second, in addition to row-oriented data format using Google's Flatbuffers, we have added support for column-oriented data formats using the Apache Arrow library within our Ceph extensions. Third, we added dynamic switching between row and column data formats within Ceph objects, a first step towards physical design management in storage systems, similar to physical design tuning in database systems.
more »
« less
- PAR ID:
- 10181971
- Date Published:
- Journal Name:
- USENIX VAULT'20
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Access libraries such as ROOT[1] and HDF5[2] allow users to interact with datasets using high level abstractions, like coordinate systems and associated slicing operations. Unfortunately, the implementations of access libraries are based on outdated assumptions about storage systems interfaces and are generally unable to fully benefit from modern fast storage devices. For example, access libraries often implement buffering and data layout that assume that large, single-threaded sequential access patterns are causing less overall latency than small parallel random access: while this is true for spinning media, it is not true for flash media. The situation is getting worse with rapidly evolving storage devices such as non-volatile memory and ever larger datasets. This project explores distributed dataset mapping infrastructures that can integrate and scale out existing access libraries using Ceph’s extensible object model, avoiding re-implementation or even modifications of these access libraries as much as possible. These programmable storage extensions coupled with our distributed dataset mapping techniques enable: 1) access library operations to be offloaded to storage system servers, 2) the independent evolution of access libraries and storage systems and 3) fully leveraging of the existing load balancing, elasticity, and failure management of distributed storage systems like Ceph. They also create more opportunities to conduct storage server-local optimizations specific to storage servers. For example, storage servers might include local key/value stores combined with chunk stores that require different optimizations than a local file system. As storage servers evolve to support new storage devices like non-volatile memory, these server-local optimizations can be implemented while minimizing disruptions to applications. We will report progress on the means by which distributed dataset mapping can be abstracted over particular access libraries, including access libraries for ROOT data, and how we address some of the challenges revolving around data partitioning and composability of access operations.more » « less
-
Ceph is an open source distributed storage system that is object-based and massively scalable. Ceph provides developers with the capability to create data interfaces that can take advantage of local CPU and memory on the storage nodes (Ceph Object Storage Devices). These interfaces are powerful for application developers and can be created in C, C++, and Lua. Skyhook is an open source storage and database project in the Center for Research in Open Source Software at UC Santa Cruz. Skyhook uses these capabilities in Ceph to create specialized read/write interfaces that leverage IO and CPU within the storage layer toward database processing and management. Specifically, we develop methods to apply predicates locally as well as additional metadata and indexing capabilities using Ceph's internal indexing mechanism built on top of RocksDB. Skyhook's approach helps to enable scale-out of a single node database system by scaling out the storage layer. Our results show the performance benefits for some queries indeed scale well as the storage layer scales out.more » « less
-
The proliferation of modern data processing tools has given rise to open-source columnar data formats. These formats help organizations avoid repeated conversion of data to a new format for each application. However, these formats are read-only, and organizations must use a heavy-weight transformation process to load data from on-line transactional processing (OLTP) systems. As a result, DBMSs often fail to take advantage of full network bandwidth when transferring data. We aim to reduce or even eliminate this overhead by developing a storage architecture for in-memory database management systems (DBMSs) that is aware of the eventual usage of its data and emits columnar storage blocks in a universal open-source format. We introduce relaxations to common analytical data formats to efficiently update records and rely on a lightweight transformation process to convert blocks to a read-optimized layout when they are cold. We also describe how to access data from third-party analytical tools with minimal serialization overhead. We implemented our storage engine based on the Apache Arrow format and integrated it into the NoisePage DBMS to evaluate our work. Our experiments show that our approach achieves comparable performance with dedicated OLTP DBMSs while enabling orders-of-magnitude faster data exports to external data science and machine learning tools than existing methods.more » « less
-
Distributed data processing ecosystems are widespread and their components are highly specialized, such that efficient interoperability is urgent. Recently, Apache Arrow was chosen by the community to serve as a format mediator, providing efficient in-memory data representation. Arrow enables efficient data movement between data processing and storage engines, significantly improving interoperability and overall performance. In this work, we design a new zero-cost data interoperability layer between Apache Spark and Arrow-based data sources through the Arrow Dataset API. Our novel data interface helps separate the computation (Spark) and data (Arrow) layers. This enables practitioners to seamlessly use Spark to access data from all Arrow Dataset API-enabled data sources and frameworks. To benefit our community, we open-source our work and show that consuming data through Apache Arrow is zero-cost: our novel data interface is either on-par or more performant than native Spark.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
