Tag Archives: ontap

Think Global, Act Local: A Buffer Cache Design for Global Ordering and Parallel Processing in the WAFL File System

Peter Denz, Matthew Curtis-Maury, Vinay Devadas. NetApp, Inc.

2016 International Conference on Parallel Processing (ICPP 2016)
Philadelphia, PA, USA

Given the enormous disparity in access speeds between main memory and storage media, modern storage servers must leverage highly effective buffer cache policies to meet demanding performance requirements. At the same time, these page replacement policies need to scale efficiently with ever-increasing core counts and memory sizes, which necessitate parallel buffer cache management. However, these requirements of effectiveness and scalability are at odds, because centralized processing does not scale with more processors and parallel policies are a challenge to implement with maximum effectiveness. We have overcome this difficulty in the NetApp® Data ONTAP® WAFL® file system by using a sophisticated technique to simultaneously allow global buffer prioritization while providing parallel management operations. In addition, we have extended the buffer cache to provide a soft isolation of different workloads’ buffer cache usage, which is akin to buffer cache quality of server (QoS). This paper presents the design and implementation of these significant extensions in the buffer cache of a high-performance commercial file system.

Resources

Systems Research and Innovation in Data ONTAP

cover.gifScott Dawkins, Kaladhar Voruganti, and John D. Strunk.

This paper introduces the December 2012 issue of OSR, which highlights some of the research and innovation that have helped us stay at the forefront of technological changes.

Over the last 20 years, there have been many changes in the data storage industry. NetApp® products have kept pace and pushed the boundary in various areas. Staying at the forefront requires attentiveness to emerging technology trends and a disciplined approach to analyzing them. By understanding the trends and how they affect our customers, we can focus our efforts on delivering the best products possible. In this issue of OSR, we highlight some of the research and innovation that have helped us stay at the forefront of these technological changes.

In ACM SIGOPS Operating Systems Review, Vol. 46, No. 3, December 2012, pp. 1-3

Resources

DataONTAP_innovation_Dawkins2.pdf

FlexVol: Flexible, Efficient File Volume Virtualization in WAFL

usenix08_button.jpgJ.K. Edwards, D. Ellard, C. Everhart, R. Fair, E. Hamilton, A. Kahn, A. Kanevsky, J. Lentini, A. Prakash, K.A. Smith, and E. Zayas.

We present the basic architecture of FlexVol volumes, including performance optimizations, and also describe the new features enabled by this architecture.

Virtualization is a well-known method of abstracting physical resources and of separating the manipulation and use of logical resources from their underlying implementation. We have used this technique to virtualize file volumes in the WAFL® file system, adding a level of indirection between client-visible volumes and the underlying physical storage. The resulting virtual file volumes, or FlexVol® volumes, are managed independent of lower storage layers. Multiple volumes can be dynamically created, deleted, resized, and reconfigured within the same physical storage container.

We also exploit this new virtualization layer to provide several powerful new capabilities. We have enhanced SnapMirror®, a tool for replicating volumes between storage systems, to remap storage allocation during transfer, thus optimizing disk layout for the destination storage system. FlexClone® volumes provide writable Snapshot® copies, using a FlexVol volume backed by a Snapshot copy of a different volume. FlexVol volumes also support thin provisioning; a FlexVol volume can have a logical size that exceeds the available physical storage. FlexClone volumes and thin provisioning are a powerful combination, as they allow the creation of light-weight copies of live data sets while consuming minimal storage resources.

We present the basic architecture of FlexVol volumes, including performance optimizations that decrease the overhead of our new virtualization layer. We also describe the new features enabled by this architecture. Our evaluation of FlexVol performance shows that it incurs only a minor performance degradation compared with traditional, nonvirtualized WAFL volumes. On the industry-standard SPEC SFS benchmark, FlexVol volumes exhibit less than 4% performance overhead, while providing all the benefits of virtualization.

In Proceedings of the USENIX Annual Technical Conference 2008 (USENIX ’08)

Resources

  • A copy of the paper is attached to this posting.

flexvol_usenix08.pdf

Data ONTAP GX: A Scalable Storage Cluster

fast07_button.jpgMichael Eisler, Peter Corbett, Michael Kazar, Daniel S. Nydick, and J. Christopher Wagner.

This paper presents Data ONTAP GX, a clustered Network Attached File server that is composed of a number of cooperating filers.

Data ONTAP GX is a clustered Network Attached File server composed of a number of cooperating filers. Each filer manages its own local file system, which consists of a number of disconnected flexible volumes. A separate namespace infrastructure runs within the cluster, which connects the volumes into one or more namespaces by means of internal junctions. The cluster collectively exposes a potentially large number of separate virtual servers, each with its own independent namespace, security and administrative domain. The cluster implements a protocol routing and translation layer which translates requests in all incoming file protocols into a single unified internal file access protocol called SpinNP. The translated requests are then forwarded to the correct filer within the cluster for servicing by the local file system instance. This provides data location transparency, which is used to support transparent data migration, load balancing, mirroring for load sharing and data protection, and fault tolerance. The cluster itself greatly simplifies the administration of a large number of filers by consolidating them into a single system image. Results from benchmarks (over one million file operations per second on a 24 node cluster) and customer experience demonstrate linear scaling.

In Proceedings of the USENIX Conference on File and Storage Technologies 2007 (FAST ’07)

Resources

  • A copy of the paper is attached to this posting.

GX-fast2007.pdf

SnapMirror®: File System Based Asynchronous Mirroring for Disaster Recovery

 

Hugo Patterson, Stephen Manley, Mike Federwisch, Dave Hitz, Steve Kleiman, and Shane Owara.

We present SnapMirror, an asynchronous mirroring technology that leverages file system snapshots to ensure the consistency of the remote mirror and optimize data transfer.

Computerized data has become critical to the survival of an enterprise. Companies must have a strategy for recovering their data should a disaster such as a fire destroy the primary data center. Current mechanisms offer data managers a stark choice: rely on affordable tape but risk the loss of a full day of data and face many hours or even days to recover, or have the benefits of a fully synchronized on-line remote mirror, but pay steep costs in both write latency and network bandwidth to maintain the mirror. In this paper, we argue that asynchronous mirroring, in which batches of updates are periodically sent to the remote mirror, can let data managers find a balance between these extremes. First, by eliminating the write latency issue, asynchrony greatly reduces the performance cost of a remote mirror. Second, by storing up batches of writes, asynchronous mirroring can avoid sending deleted or overwritten data and thereby reduce network bandwidth requirements. Data managers can tune the update frequency to trade network bandwidth against the potential loss of more data. We present SnapMirror, an asynchronous mirroring technology that leverages file system snapshots to ensure the consistency of the remote mirror and optimize data transfer. We use traces of production filers to show that even updating an asynchronous mirror every 15 minutes can reduce data transferred by 30% to 80%. We find that exploiting file system knowledge of deletions is critical to achieving any reduction for no-overwrite file systems such as WAFL and LFS. Experiments on a running system show that using file system metadata can reduce the time to identify changed blocks from minutes to seconds compared to purely logical approaches. Finally, we show that using SnapMirror to update every 30 minutes increases the response time of a heavily loaded system only 22%.

In Proceedings of the USENIX Conference on File and Storage Technologies 2002 (FAST ’02)

Resources

  • A copy of the paper is attached to this posting.

snapmirror-fast02.pdf

Logical vs. Physical File System Backup

OSDI99.gifNorman C. Hutchinson, Stephen Manley, Mike Federwisch, Guy Harris, Dave Hitz, Steven Kleiman, and Sean O’Malley.

This paper compares logical and physical backup strategies in large file systems.

As file systems grow in size, ensuring that data is safely stored becomes more and more difficult. Historically, file system backup strategies have focused on logical backup where files are written in their entirety to the backup media. An alternative is physical backup where the disk blocks that make up the file system are written to the backup media. This paper compares logical and physical backup strategies in large file systems. We discuss the advantages and disadvantages of the two approaches, and conclude by showing that while both can achieve good performance, physical backup and restore can achieve much higher throughput while consuming less CPU. In addition, physical backup and restore is much more capable of scaling its performance as more devices are added to a system.

In Proceedings of the 3rd Symposium on Operating Systems Design and Implementation 1999 (OSDI ’99)

Resources

  • A copy of the paper is attached to this posting.

logical-backup-osdi99.pdf

File System Design for an NFS File Server Appliance

 

Dave Hitz, James Lau, and Michael Malcolm.

This paper describes WAFL (Write Anywhere File Layout) and how WAFL uses Snapshots to eliminate the need for file system consistency checking after an unclean shutdown.

Network Appliance Corporation recently began shipping a new kind of network server called an NFS file server appliance, which is a dedicated server whose sole function is to provide NFS file service. The file system requirements for an NFS appliance are different from those for a general-purpose UNIX system, both because an NFS appliance must be optimized for network file access and because an appliance must be easy to use.

This paper describes WAFL (Write Anywhere File Layout), which is a file system designed specifically to work in an NFS appliance. The primary focus is on the algorithms and data structures that WAFL uses to implement Snapshots™, which are read-only clones of the active file system. WAFL uses a copy-on-write technique to minimize the disk space that Snapshots consume. This paper also describes how WAFL uses Snapshots to eliminate the need for file system consistency checking after an unclean shutdown.

In Proceedings of the USENIX Winter 1994 Technical Conference

Resources

  • A copy of the paper is attached to this posting.
  • A copy of a technical report (better formatting of the paper) is attached to this posting

FILE_SYSTEM_DESIGN_USENIX94.pdf

file-system-design.pdf