Hardware Recommendations
==========================
-Ceph runs on commodity hardware and a Linux operating system over a TCP/IP
-network. The hardware recommendations for different processes/daemons differ
-considerably.
-
-* **OSDs:** OSD hosts should have ample data storage in the form of a hard drive
- or a RAID. Ceph OSDs run the RADOS service, calculate data placement with
- CRUSH, and maintain their own copy of the cluster map. Therefore, OSDs
- should have a reasonable amount of processing power.
-
-* **Monitors:** Ceph monitor hosts require enough disk space for the cluster map,
- but usually do not encounter heavy loads. Monitor hosts do not need to be
- very powerful.
+Ceph was designed to run on commodity hardware, which makes building and
+maintaining petabyte-scale data clusters economically feasible.
+When planning out your cluster hardware, you will need to balance a number
+of considerations, including failure domains and potential performance
+issues. Hardware planning should include distributing Ceph daemons and
+other processes that use Ceph across many hosts. Generally, we recommend
+running Ceph daemons of a specific type on a host configured for that type
+of daemon. We recommend using other hosts for processes that utilize your
+data cluster (e.g., OpenStack, CloudStack, etc).
+
+- **CPU**: Ceph metadata servers dynamically redistribute their load, which is
+ CPU intensive. So your metadata servers should have significant processing power
+ (e.g., quad core or better CPUs). Ceph OSDs run the RADOS service, calculate
+ data placement with CRUSH, replicate data, and maintain their own copy of the
+ cluster map. Therefore, OSDs should have a reasonable amount of processing power
+ (e.g., dual-core processors). Monitors simply maintain a master copy of the
+ cluster map, so they are not CPU intensive. You must also consider whether the
+ host machine will run CPU-intensive processes in addition to Ceph daemons. For
+ example, if your hosts will run computing VMs (e.g., OpenStack Nova), you will
+ need to ensure that these other processes leave sufficient processing power for
+ Ceph daemons. We recommend running additional CPU-intensive processes on
+ separate hosts.
+
+- **RAM**: Metadata servers and monitors must be capable of serving their data
+ quickly, so they should have plenty of RAM (e.g., 1GB of RAM per daemon
+ instance). OSDs do not require as much RAM (e.g., 500MB of RAM per daemon
+ instance). Generally, more RAM is better.
+
+- **Data Storage**: Plan your data storage configuration carefully, because
+ there are significant opportunities for performance improvement by incurring
+ the added cost of using solid state drives, and there are significant
+ cost-per-gigabyte considerations with hard disk drives. Metadata servers and monitors
+ don't use a lot of storage space. A metadata server requires approximately 1MB
+ of storage space per daemon instance. A monitor requires approximately 10GB of
+ storage space per daemon instance. One opportunity for performance improvement
+ is to use solid-state drives to reduce random access time and read latency while
+ accelerating throughput. Solid state drives cost more than 10x as much per
+ gigabyte when compared to a hard disk, but they often exhibit access times that
+ are at least 100x faster than a hard disk drive. Since the storage requirements for
+ metadata servers and monitors are so low, solid state drives may provide an
+ economical opportunity to improve performance. OSDs should have plenty of disk
+ space. We recommend a minimum disk size of 1 terabyte. We recommend dividing the
+ price of the hard disk drive by the number of gigabytes to arrive at a cost per
+ gigabyte, because larger drives may have a significant impact on the
+ cost-per-gigabyte. For example, a 1 terabyte hard disk priced at $75.00 has a cost
+ of $0.07 per gigabyte (i.e., $75 / 1024 = 0.0732). By contrast, a 3 terabyte hard
+ disk priced at $150.00 has a cost of $0.05 per gigabyte (i.e., $150 / 3072 = 0.0488).
+ In the foregoing example, using the 1 terabyte disks would generally increase the cost
+ per gigabyte by 40%--rendering your cluster substantially less cost efficient.
+ For OSD hosts, we recommend using an OS disk for the operating
+ system and software, and one disk for each OSD daemon you run on the host. While
+ solid state drives are cost prohibitive for object storage, OSDs may see a
+ performance improvement by storing an OSD's journal on a solid state drive and
+ the OSD's object data on a hard disk drive. You may run multiple OSDs per host,
+ but you should ensure that the sum of the total throughput of your OSD hard
+ disks doesn't exceed the network bandwidth required to service a client's need
+ to read or write data. You should also consider what percentage of the cluster's
+ data storage is on each host. If the percentage is large and the host fails, it
+ can lead to problems such as exceeding the ``full ratio``, which causes Ceph to
+ halt operations as a safety precaution that prevents data loss.
-* **Metadata Servers:** Ceph metadata servers distribute their load. However,
- metadata servers must be capable of serving their data quickly. Metadata
- servers should have strong processing capability and plenty of RAM.
+- **Networks**: We recommend that each host have at least two 1Gbps network interface
+ controllers (NICs). Since most commodity hard disk drives have a throughput of
+ approximately 100MB/sec., your NICs should be able to handle the traffic for
+ the OSD disks on your host. We recommend a minimum of two NICs to account for a
+ public (front-side) network and a cluster (back-side) network. A cluster network
+ (preferably not connected to the internet) handles the additional load for data
+ replication and helps stop denial of service attacks that prevent the cluster
+ from achieving ``active + clean`` states for placement groups as OSDs replicate
+ data across the cluster. Consider starting with a 10Gbps network in your racks.
+ Replicating 1TB of data across a 1Gbps network takes 3 hours, and 3TBs (a typical
+ drive configuration) takes 9 hours. By contrast, with a 10Gbps network, the
+ replication times would be 20 minutes and 1 hour respectively. In a petabyte-scale
+ cluster, failure of an OSD disk should be an expectation, not an exception.
+ System administrators will appreciate PGs recovering from a ``degraded`` state
+ to an ``active + clean`` state as rapidly as possible, with price / performance
+ tradeoffs taken into consideration. Top-of-rack routers for each network need to
+ be able to communicate with spine routers that have even faster throughput--e.g.,
+ 40Gbps to 100Gbps. Some experts suggest using a third NIC per host for a management
+ network (e.g., hypervisor SSH access, VM image uploads, management sockets, etc.),
+ and potentially a fourth NIC per host to handle VM traffic between between the cluster
+ and compute stacks (e.g., OpenStack, CloudStack, etc.). Running three or four
+ logical networks may seem like overkill, but each traffic path represents a
+ potential capacity, throughput and/or performance bottleneck that you should
+ carefully consider before deploying a large scale data cluster.
+
+- **Failure Domains**: A failure domain is any failure that prevents access
+ to one or more OSDs. That could be a stopped daemon on a host; a hard disk failure,
+ an OS crash, a malfunctioning NIC, a failed power supply, a network outage, a power
+ outage, and so forth. When planning out your hardware needs, you must balance the
+ temptation to reduce costs by placing too many responsibilities into too few failure
+ domains, and the added costs of isolating every potential failure domain.
+
+`Inktank`_ provides excellent premium support for hardware planning.
+
+.. _Inktank: http://www.inktank.com
-.. note:: If you are not using the Ceph File System, you do not need a meta data server.
Minimum Hardware Recommendations
================================
+--------------+----------------+------------------------------------+
| Process | Criteria | Minimum Recommended |
+==============+================+====================================+
-| ``ceph-osd`` | Processor | 64-bit AMD-64/i386 dual-core |
+| ``ceph-osd`` | Processor | 1x 64-bit AMD-64/i386 dual-core |
| +----------------+------------------------------------+
| | RAM | 500 MB per daemon |
| +----------------+------------------------------------+
-| | Volume Storage | 1-disk or RAID per daemon |
+| | Volume Storage | 1x Disk per daemon |
| +----------------+------------------------------------+
-| | Network | 2-1GB Ethernet NICs |
+| | Network | 2x 1GB Ethernet NICs |
+--------------+----------------+------------------------------------+
-| ``ceph-mon`` | Processor | 64-bit AMD-64/i386 |
+| ``ceph-mon`` | Processor | 1x 64-bit AMD-64/i386 |
| +----------------+------------------------------------+
| | RAM | 1 GB per daemon |
| +----------------+------------------------------------+
| | Disk Space | 10 GB per daemon |
| +----------------+------------------------------------+
-| | Network | 2-1GB Ethernet NICs |
+| | Network | 2x 1GB Ethernet NICs |
+--------------+----------------+------------------------------------+
-| ``ceph-mds`` | Processor | 64-bit AMD-64/i386 quad-core |
+| ``ceph-mds`` | Processor | 1x 64-bit AMD-64/i386 quad-core |
| +----------------+------------------------------------+
| | RAM | 1 GB minimum per daemon |
| +----------------+------------------------------------+
| | Disk Space | 1 MB per daemon |
| +----------------+------------------------------------+
-| | Network | 2-1GB Ethernet NICs |
+| | Network | 2x 1GB Ethernet NICs |
+--------------+----------------+------------------------------------+
.. important: If you are running an OSD with a single disk, create a
+----------------+----------------+------------------------------------+
| Configuration | Criteria | Minimum Recommended |
+================+================+====================================+
-| Dell PE R510 | Processor | 2 64-bit quad-core Xeon CPUs |
+| Dell PE R510 | Processor | 2x 64-bit quad-core Xeon CPUs |
| +----------------+------------------------------------+
| | RAM | 16 GB |
| +----------------+------------------------------------+
-| | Volume Storage | 8-2TB drives. 1-OS 7-Storage |
+| | Volume Storage | 8x 2TB drives. 1 OS, 7 Storage |
| +----------------+------------------------------------+
-| | Client Network | 2-1GB Ethernet NICs |
+| | Client Network | 2x 1GB Ethernet NICs |
| +----------------+------------------------------------+
-| | OSD Network | 2-1GB Ethernet NICs |
+| | OSD Network | 2x 1GB Ethernet NICs |
| +----------------+------------------------------------+
-| | NIC Mgmt. | 2-1GB Ethernet NICs |
+| | NIC Mgmt. | 2x 1GB Ethernet NICs |
+----------------+----------------+------------------------------------+
-| Dell PE R515 | Processor | 1 hex-core Opteron CPU |
+| Dell PE R515 | Processor | 1x hex-core Opteron CPU |
| +----------------+------------------------------------+
| | RAM | 16 GB |
| +----------------+------------------------------------+
-| | Volume Storage | 12-3TB drives. Storage |
+| | Volume Storage | 12x 3TB drives. Storage |
| +----------------+------------------------------------+
-| | OS Storage | 1-500GB drive. Operating System. |
+| | OS Storage | 1x 500GB drive. Operating System. |
| +----------------+------------------------------------+
-| | Client Network | 2-1GB Ethernet NICs |
+| | Client Network | 2x 1GB Ethernet NICs |
| +----------------+------------------------------------+
-| | OSD Network | 2-1GB Ethernet NICs |
+| | OSD Network | 2x 1GB Ethernet NICs |
| +----------------+------------------------------------+
-| | NIC Mgmt. | 2-1GB Ethernet NICs |
+| | NIC Mgmt. | 2x 1GB Ethernet NICs |
+----------------+----------------+------------------------------------+
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projects / ceph.git / commitdiff