80 lines
4.7 KiB
XML
80 lines
4.7 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE section [
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<!ENTITY % openstack SYSTEM "entities/openstack.ent">
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%openstack;
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]>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="section_objectstorage-cluster-architecture">
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<title>Cluster architecture</title>
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<section xml:id="section_access-tier">
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<title>Access tier</title>
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<para>Large-scale deployments segment off an access tier, which is considered the Object Storage
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system's central hub. The access tier fields the incoming API requests from clients and
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moves data in and out of the system. This tier consists of front-end load balancers,
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ssl-terminators, and authentication services. It runs the (distributed) brain of the
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Object Storage system: the proxy server processes.</para>
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<figure>
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<title>Object Storage architecture</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="../common/figures/objectstorage-arch.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para>Because access servers are collocated in their own tier, you can scale out read/write
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access regardless of the storage capacity. For example, if a cluster is on the public
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Internet, requires SSL termination, and has a high demand for data access, you can
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provision many access servers. However, if the cluster is on a private network and used
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primarily for archival purposes, you need fewer access servers.</para>
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<para>Since this is an HTTP addressable storage service, you may incorporate a load balancer
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into the access tier.</para>
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<para>Typically, the tier consists of a collection of 1U servers. These machines use a
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moderate amount of RAM and are network I/O intensive. Since these systems field each
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incoming API request, you should provision them with two high-throughput (10GbE)
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interfaces - one for the incoming "front-end" requests and the other for the "back-end"
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access to the object storage nodes to put and fetch data.</para>
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<section xml:id="section_access-tier-considerations">
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<title>Factors to consider</title>
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<para>For most publicly facing deployments as well as private deployments available
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across a wide-reaching corporate network, you use SSL to encrypt traffic to the
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client. SSL adds significant processing load to establish sessions between clients,
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which is why you have to provision more capacity in the access layer. SSL may not be
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required for private deployments on trusted networks.</para>
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</section>
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</section>
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<section xml:id="section_storage-nodes">
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<title>Storage nodes</title>
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<para>In most configurations, each of the five zones should have an equal amount of storage
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capacity. Storage nodes use a reasonable amount of memory and CPU. Metadata needs to be
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readily available to return objects quickly. The object stores run services not only to
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field incoming requests from the access tier, but to also run replicators, auditors, and
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reapers. You can provision object stores provisioned with single gigabit or 10 gigabit
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network interface depending on the expected workload and desired performance.</para>
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<figure>
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<title>Object Storage (swift)</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="../common/figures/objectstorage-nodes.png"/>
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</imageobject>
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</mediaobject>
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</figure>
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<para>Currently, a 2 TB or 3 TB SATA disk delivers
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good performance for the price. You can use desktop-grade
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drives if you have responsive remote hands in the datacenter
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and enterprise-grade drives if you don't.</para>
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<section xml:id="section_storage-nodes-considerations">
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<title>Factors to consider</title>
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<para>You should keep in mind the desired I/O performance for single-threaded requests .
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This system does not use RAID, so a single disk handles each request for an object.
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Disk performance impacts single-threaded response rates.</para>
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<para>To achieve apparent higher throughput, the object storage system is designed to
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handle concurrent uploads/downloads. The network I/O capacity (1GbE, bonded 1GbE
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pair, or 10GbE) should match your desired concurrent throughput needs for reads and
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writes.</para>
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</section>
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</section>
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</section>
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