================ Deployment Guide ================ ----------------------- Hardware Considerations ----------------------- Swift is designed to run on commodity hardware. At Rackspace, our storage servers are currently running fairly generic 4U servers with 24 2T SATA drives and 8 cores of processing power. RAID on the storage drives is not required and not recommended. Swift's disk usage pattern is the worst case possible for RAID, and performance degrades very quickly using RAID 5 or 6. ------------------ Deployment Options ------------------ The swift services run completely autonomously, which provides for a lot of flexibility when architecting the hardware deployment for swift. The 4 main services are: #. Proxy Services #. Object Services #. Container Services #. Account Services The Proxy Services are more CPU and network I/O intensive. If you are using 10g networking to the proxy, or are terminating SSL traffic at the proxy, greater CPU power will be required. The Object, Container, and Account Services (Storage Services) are more disk and network I/O intensive. The easiest deployment is to install all services on each server. There is nothing wrong with doing this, as it scales each service out horizontally. At Rackspace, we put the Proxy Services on their own servers and all of the Storage Services on the same server. This allows us to send 10g networking to the proxy and 1g to the storage servers, and keep load balancing to the proxies more manageable. Storage Services scale out horizontally as storage servers are added, and we can scale overall API throughput by adding more Proxies. If you need more throughput to either Account or Container Services, they may each be deployed to their own servers. For example you might use faster (but more expensive) SAS or even SSD drives to get faster disk I/O to the databases. Load balancing and network design is left as an excercise to the reader, but this is a very important part of the cluster, so time should be spent designing the network for a Swift cluster. .. _ring-preparing: ------------------ Preparing the Ring ------------------ The first step is to determine the number of partitions that will be in the ring. We recommend that there be a minimum of 100 partitions per drive to insure even distribution accross the drives. A good starting point might be to figure out the maximum number of drives the cluster will contain, and then multiply by 100, and then round up to the nearest power of two. For example, imagine we are building a cluster that will have no more than 5,000 drives. That would mean that we would have a total number of 500,000 partitions, which is pretty close to 2^19, rounded up. It is also a good idea to keep the number of partitions small (realatively). The more partitions there are, the more work that has to be done by the replicators and other backend jobs and the more memory the rings consume in process. The goal is to find a good balance between small rings and maximum cluster size. The next step is to determine the number of replicas to store of the data. Currently it is recommended to use 3 (as this is the only value that has been tested). The higher the number, the more storage that is used but the less likely you are to lose data. It is also important to determine how many zones the cluster should have. It is recommended to start with a minimum of 5 zones. You can start with fewer, but our testing has shown that having at least five zones is optimal when failures occur. We also recommend trying to configure the zones as high a level as possible to create as much isolation as possible. Some example things to take into consideration can include physical location, power availability, and network connectivity. For example, in a small cluster you might decide to split the zones up by cabinet, with each cabinet having its own power and network connectivity. The zone concept is very abstract, so feel free to use it in whatever way best isolates your data from failure. Zones are referenced by number, beginning with 1. You can now start building the ring with:: swift-ring_builder create This will start the ring build process creating the with 2^ partitions. is the time in hours before a specific partition can be moved in succession (24 is a good value for this). Devices can be added to the ring with:: swift-ring_builder add z-:/_ This will add a device to the ring where is the name of the builder file that was created previously, is the number of the zone this device is in, is the ip address of the server the device is in, is the port number that the server is running on, is the name of the device on the server (for example: sdb1), is a string of metadata for the device (optional), and is a float weight that determines how many partitions are put on the device relative to the rest of the devices in the cluster (a good starting point is 100.0 x TB on the drive). Add each device that will be initially in the cluster. Once all of the devices are added to the ring, run:: swift_ring_builder rebalance This will distribute the partitions across the drives in the ring. It is important whenever making changes to the ring to make all the changes required before running rebalance. This will ensure that the ring stays as balanced as possible, and as few partitions are moved as possible. The above process should be done to make a ring for each storage serivce (Account, Container and Object). The builder files will be needed in future changes to the ring, so it is very important that these be kept and backed up. The resulting .tar.gz ring file should be pushed to all of the servers in the cluster. For more information about building rings, running swift_ring_builder with no options will display help text with available commands and options. More information on how the ring works internally can be found in the :doc:`Ring Overview `. --------------------------- Object Server Configuration --------------------------- An Example Object Server configuration can be found at etc/object-server.conf-sample in the source code repository. The following configuration options are available: [object-server] ================== ========== ============================================= Option Default Description ------------------ ---------- --------------------------------------------- swift_dir /etc/swift Swift configuration directory devices /srv/node Parent directory of where devices are mounted mount_check true Weather or not check if the devices are mounted to prevent accidently writing to the root device bind_ip 0.0.0.0 IP Address for server to bind to bind_port 6000 Port for server to bind to workers 1 Number of workers to fork log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level log_requests True Weather or not to log each request user swift User to run as node_timeout 3 Request timeout to external services conn_timeout 0.5 Connection timeout to external services network_chunk_size 65536 Size of chunks to read/write over the network disk_chunk_size 65536 Size of chunks to read/write to disk max_upload_time 86400 Maximum time allowed to upload an object slow 0 If > 0, Minimum time in seconds for a PUT or DELETE request to complete ================== ========== ============================================= [object-replicator] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level daemonize yes Weather or not to run replication as a daemon run_pause 30 Time in seconds to wait between replication passes concurrency 1 Number of replication workers to spawn timeout 5 Timeout value sent to rsync --timeout and --contimeout options stats_interval 3600 Interval in seconds between logging replication statistics reclaim_age 604800 Time elapsed in seconds before an object can be reclaimed ================== ========== =========================================== [object-updater] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level interval 300 Minimum time for a pass to take concurrency 1 Number of updater workers to spawn node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services slowdown 0.01 Time in seconds to wait between objects ================== ========== =========================================== [object-auditor] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level interval 1800 Minimum time for a pass to take node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services ================== ========== =========================================== ------------------------------ Container Server Configuration ------------------------------ An example Container Server configuration can be found at etc/container-server.conf-sample in the source code repository. The following configuration options are available: [container-server] ================== ========== ============================================ Option Default Description ------------------ ---------- -------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level swift_dir /etc/swift Swift configuration directory devices /srv/node Parent irectory of where devices are mounted mount_check true Weather or not check if the devices are mounted to prevent accidently writing to the root device bind_ip 0.0.0.0 IP Address for server to bind to bind_port 6001 Port for server to bind to workers 1 Number of workers to fork user swift User to run as node_timeout 3 Request timeout to external services conn_timeout 0.5 Connection timeout to external services ================== ========== ============================================ [container-replicator] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level per_diff 1000 concurrency 8 Number of replication workers to spawn run_pause 30 Time in seconds to wait between replication passes node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services reclaim_age 604800 Time elapsed in seconds before a container can be reclaimed ================== ========== =========================================== [container-updater] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level interval 300 Minimum time for a pass to take concurrency 4 Number of updater workers to spawn node_timeout 3 Request timeout to external services conn_timeout 0.5 Connection timeout to external services slowdown 0.01 Time in seconds to wait between containers ================== ========== =========================================== [container-auditor] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level interval 1800 Minimum time for a pass to take node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services ================== ========== =========================================== ---------------------------- Account Server Configuration ---------------------------- An example Account Server configuration can be found at etc/account-server.conf-sample in the source code repository. The following configuration options are available: [account-server] ================== ========== ============================================= Option Default Description ------------------ ---------- --------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level swift_dir /etc/swift Swift configuration directory devices /srv/node Parent directory or where devices are mounted mount_check true Weather or not check if the devices are mounted to prevent accidently writing to the root device bind_ip 0.0.0.0 IP Address for server to bind to bind_port 6002 Port for server to bind to workers 1 Number of workers to fork user swift User to run as ================== ========== ============================================= [account-replicator] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level per_diff 1000 concurrency 8 Number of replication workers to spawn run_pause 30 Time in seconds to wait between replication passes node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services reclaim_age 604800 Time elapsed in seconds before a account can be reclaimed ================== ========== =========================================== [account-auditor] ==================== ========== =========================================== Option Default Description -------------------- ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level interval 1800 Minimum time for a pass to take max_container_count 100 Maximum containers randomly picked for a given account audit node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services ==================== ========== =========================================== [account-reaper] ================== ========== =========================================== Option Default Description ------------------ ---------- ------------------------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Logging level concurrency 25 Number of replication workers to spawn interval 3600 Minimum time for a pass to take node_timeout 10 Request timeout to external services conn_timeout 0.5 Connection timeout to external services ================== ========== =========================================== -------------------------- Proxy Server Configuration -------------------------- [proxy-server] ============================ =============== ============================= Option Default Description ---------------------------- --------------- ----------------------------- log_facility LOG_LOCAL0 Syslog log facility log_level INFO Log level bind_ip 0.0.0.0 IP Address for server to bind to bind_port 80 Port for server to bind to cert_file Path to the ssl .crt key_file Path to the ssl .key swift_dir /etc/swift Swift configuration directory log_headers True If True, log headers in each request workers 1 Number of workers to fork user swift User to run as recheck_account_existence 60 Cache timeout in seconds to send memcached for account existance recheck_container_existence 60 Cache timeout in seconds to send memcached for container existance object_chunk_size 65536 Chunk size to read from object servers client_chunk_size 65536 Chunk size to read from clients memcache_servers 127.0.0.1:11211 Comma separated list of memcached servers ip:port node_timeout 10 Request timeout to external services client_timeout 60 Timeout to read one chunk from a client conn_timeout 0.5 Connection timeout to external services error_suppression_interval 60 Time in seconds that must elapse since the last error for a node to be considered no longer error limited error_suppression_limit 10 Error count to consider a node error limited rate_limit 20000.0 Max container level ops per second account_rate_limit 200.0 Max account level ops per second rate_limit_account_whitelist Comma separated list of account name hashes to not rate limit rate_limit_account_blacklist Comma separated list of account name hashes to block completly ============================ =============== ============================= [auth-server] ============ =================================== ======================== Option Default Description ------------ ----------------------------------- ------------------------ class swift.common.auth.DevAuthMiddleware Auth wsgi middleware to use ip 127.0.0.1 IP address of auth server port 11000 Port of auth server node_timeout 10 Request timeout ============ =================================== ======================== ------------------------ Memcached Considerations ------------------------ Several of the Services rely on Memcached for caching certain types of lookups, such as auth tokens, and container/account existance. Swift does not do any caching of actual object data. Memcached should be able to run on any servers that have available RAM and CPU. At Rackspace, we run Memcached on the proxy servers. The `memcache_servers` config option in the `proxy-server.conf` should contain all memcached servers. ----------- System Time ----------- Time may be relative but it is relatively important for Swift! Swift uses timestamps to determine which is the most recent version of an object. It is very important for the system time on each server in the cluster to by synced as closely as possible (more so for the proxy server, but in general it is a good idea for all the servers). At Rackspace, we use NTP with a local NTP server to ensure that the system times are as close as possible. This should also be monitored to ensure that the times do not vary too much. ---------------------- General Service Tuning ---------------------- Most services support either a worker or concurrency value in the settings. This allows the services to make effective use of the cores available. A good starting point to set the concurrency level for the proxy and storage services to 2 times the number of cores available. If more than one service is sharing a server, then some experimentaiton may be needed to find the best balance. At Rackspace, our Proxy servers have dual quad core processors, giving us 8 cores. Our testing has shown 16 workers to be a pretty good balance when saturating a 10g network and gives good CPU utilization. Our Storage servers all run together on the same servers. These servers have dual quad core processors, for 8 cores total. We run the Account, Container, and Object servers with 8 workers each. Most of the background jobs are run at a concurrency of 1, with the exception of the replicators which are run at a concurrency of 2. The above configuration setting should be taken as suggestions and testing of configuration settings should be done to ensure best utilization of CPU, network connectivity, and disk I/O. ------------------------- Filesystem Considerations ------------------------- Swift is designed to be mostly filesystem agnostic--the only requirement beeing that the filesystem supports extended attributes (xattrs). After thorough testing with our use cases and hardware configurations, XFS was the best all-around choice. If you decide to use a filesystem other than XFS, we highly recommend thorough testing. If you are using XFS, some settings that can dramatically impact performance. We recommend the following when creating the XFS partition:: mkfs.xfs -i size=1024 -f /dev/sda1 Setting the inode size is important, as XFS stores xattr data in the inode. If the metadata is too large to fit in the inode, a new extent is created, which can cause quite a performance problem. Upping the inode size to 1024 bytes provides enough room to write the default metadata, plus a little headroom. We do not recommend running Swift on RAID, but if you are using RAID it is also important to make sure that the proper sunit and swidth settings get set so that XFS can make most efficient use of the RAID array. We also recommend the following example mount options when using XFS:: mount -t xfs -o noatime,nodiratime,nobarrier,logbufs=8 /dev/sda1 /srv/node/sda For a standard swift install, all data drives are mounted directly under /srv/node (as can be seen in the above example of mounting /def/sda1 as /srv/node/sda). If you choose to mount the drives in another directory, be sure to set the `devices` config option in all of the server configs to point to the correct directory. --------------------- General System Tuning --------------------- Rackspace currently runs Swift on Ubuntu Server 10.04, and the following changes have been found to be useful for our use cases. The following settings should be in `/etc/sysctl.conf`:: # disable TIME_WAIT.. wait.. net.ipv4.tcp_tw_recycle=1 net.ipv4.tcp_tw_reuse=1 # disable syn cookies net.ipv4.tcp_syncookies = 0 # double amount of allowed conntrack net.ipv4.netfilter.ip_conntrack_max = 262144 To load the updated sysctl settings, run ``sudo sysctl -p`` A note about changing the TIME_WAIT values. By default the OS will hold a port open for 60 seconds to ensure that any remaining packets can be received. During high usage, and with the number of connections that are created, it is easy to run out of ports. We can change this since we are in control of the network. If you are not in control of the network, or do not expect high loads, then you may not want to adjust those values. ---------------------- Logging Considerations ---------------------- Swift is set up to log directly to syslog. Every service can be configured with the `log_facility` option to set the syslog log facility destination. It is recommended to use syslog-ng to route the logs to specific log files locally on the server and also to remote log collecting servers.