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Best practices for selecting an external NTP time

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KB ID: 3013657 Version: 2.0 Published date: 06/20/2014 Views: 928

Answer

Background:

StorageGRID comprises of a distributed set of services, mostly running on separate hardware. Thisdistributed nature requires a precise and tight timing of the underlying hardware; if the clocks on theservers deviate too much, StorageGRID will sever communication to the outlying node(s).

Timing is so important to the StorageGRID functionality that the NTP service is a dependency for allother grid services; the servermanager will not bring any other services online if NTP does not startsuccessfully. In fact, this is utilized in the maintenance procedures. It is possible to prevent an auto-startup of the StorageGRID software by creating a 0-byte file: /etc/sv/ntp/DoNotStart

A best practice for installing StorageGRID is to configure NTP in a hierarchical manner - the Control Nodes are configured for time synchronization with external time sources. They are also configured assynchronizing peers (that is, the Control Nodes synchronize with each other as well as the externalsources). All other nodes within the StorageGRID use Control Nodes as their time sources.

If a sufficient number of Control Nodes deviate from the external time sources, the entire grid might begin to drift away from the external time sources.

Dramatic time drifts from the configured sources are referred to as 'fly-wheeling', and can affect either single nodes or the whole grid.

To ensure the best possible conditions for StorageGRID to maintain time precision and accuracy, NTPconfiguration should adhere to the following best practices:

Use Stratum 1 time sources. Stratum 0 are generally atomic or radio clocks that are not accessible

through the network. Stratum 1 sources are servers directly connected to the Stratum 0 sourcesand are therefore the most accurate NTP sources available. A complete description of NTP stratais available on the Wikipedia NTP page.Use at least 5 Stratum 1 sources. Using multiple sources increases the probability of an NTP lock in the event of upstream network disruptions.Choose geographically local sources when selecting. This will reduce both the network latencyand the likelihood of network disruption to a given source.Always test the connectivity to a new time source before incorporating it into the NTPconfiguration.Use these resources to locate additional NTP sources:

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NIST Internet Time ServersUSNO NTP Network Time Servers

For more information, see Selecting Offsite NTP Servers.

At the time of writing, the following NTP Stratum 1 sources are commonly used in StorageGRIDdeployments:

Pacific Time Zone

tick.ucla.edu (164.67.62.194)utcnist.colorado.edu (128.138.140.44)timekeeper.isi.edu (128.9.176.30)usno.pa‐x.dec.com (204.123.2.72)

Mountain Time Zone

utcnist.colorado.edu (128.138.140.44)utcnist2.colorado.edu (128.138.141.172)usno.pa‐x.dec.com (204.123.2.72)

Central Time Zone

time.nist.gov (192.43.244.18)nist1‐lnk.binary.net (216.229.0.179)nist.time.nosc.us (96.226.123.117)

Eastern Time Zone

navobs1.gatech.edu (130.207.244.240)nist1‐ny.ustiming.org (64.90.182.55)nist1‐nj.ustiming.org (96.47.67.105)

Disclaimer

NetApp provides no representations or warranties regarding the accuracy, reliability, or serviceabilityof any information or recommendations provided in this publication, or with respect to any results thatmay be obtained by the use of the information or observance of any recommendations provided herein.The information in this document is distributed AS IS, and the use of this information or theimplementation of any recommendations or techniques herein is a customer’s responsibility anddepends on the customer’s ability to evaluate and integrate them into the customer’s operationalenvironment. This document and the information contained herein may be used solely in connectionwith the NetApp products discussed in this document.