I’m running PostgreSQL 9.6.3 on Ubuntu 16.10 (kernel 4.4.0-85-generic). Hardware is:
*2x Intel Xeon E5550 *72GB RAM *Hardware RAID10 (4 x 146GB SAS 10k) P410i controller with 1GB FBWC (80% read/20% write) for Postgresql data only: Logical Drive: 3 Size: 273.4 GB Fault Tolerance: 1+0 Heads: 255 Sectors Per Track: 32 Cylinders: 65535 Strip Size: 128 KB Full Stripe Size: 256 KB Status: OK Caching: Enabled Unique Identifier: 600508B1001037383941424344450A00 Disk Name: /dev/sdc Mount Points: /mnt/data 273.4 GB OS Status: LOCKED Logical Drive Label: A00A194750123456789ABCDE516F Mirror Group 0: physicaldrive 2I:1:5 (port 2I:box 1:bay 5, SAS, 146 GB, OK) physicaldrive 2I:1:6 (port 2I:box 1:bay 6, SAS, 146 GB, OK) Mirror Group 1: physicaldrive 2I:1:7 (port 2I:box 1:bay 7, SAS, 146 GB, OK) physicaldrive 2I:1:8 (port 2I:box 1:bay 8, SAS, 146 GB, OK) Drive Type: Data Formatted with ext4 with: sudo mkfs.ext4 -E stride=32,stripe_width=64 -v /dev/sdc1. Mounted in /etc/fstab with this line: "UUID=99fef4ae-51dc-4365-9210-0b153b1cbbd0 /mnt/data ext4 rw,nodiratime,user_xattr,noatime,nobarrier,errors=remount-ro 0 1" Postgresql is the only application running on this server. Postgresql is used as a mini data warehouse to generate reports and do statistical analysis. It is used by at most 2 users and fresh data is added every 10 days. The database has 16 tables: one is 224GB big and the rest are between 16kB and 470MB big. My configuration is: name | current_setting | source ---------------------------------+------------------------------------------------+---------------------- application_name | psql | client autovacuum_vacuum_scale_factor | 0 | configuration file autovacuum_vacuum_threshold | 2000 | configuration file checkpoint_completion_target | 0.9 | configuration file checkpoint_timeout | 30min | configuration file client_encoding | UTF8 | client client_min_messages | log | configuration file cluster_name | 9.6/main | configuration file cpu_index_tuple_cost | 0.001 | configuration file cpu_operator_cost | 0.0005 | configuration file cpu_tuple_cost | 0.003 | configuration file DateStyle | ISO, YMD | configuration file default_statistics_target | 100 | configuration file default_text_search_config | pg_catalog.english | configuration file dynamic_shared_memory_type | posix | configuration file effective_cache_size | 22GB | configuration file effective_io_concurrency | 4 | configuration file external_pid_file | /var/run/postgresql/9.6-main.pid | configuration file lc_messages | C | configuration file lc_monetary | en_CA.UTF-8 | configuration file lc_numeric | en_CA.UTF-8 | configuration file lc_time | en_CA.UTF-8 | configuration file listen_addresses | * | configuration file lock_timeout | 100s | configuration file log_autovacuum_min_duration | 0 | configuration file log_checkpoints | on | configuration file log_connections | on | configuration file log_destination | csvlog | configuration file log_directory | /mnt/bigzilla/data/toburn/hp/postgresql/pg_log | configuration file log_disconnections | on | configuration file log_error_verbosity | default | configuration file log_file_mode | 0600 | configuration file log_filename | postgresql-%Y-%m-%d_%H%M%S.log | configuration file log_line_prefix | user=%u,db=%d,app=%aclient=%h | configuration file log_lock_waits | on | configuration file log_min_duration_statement | 0 | configuration file log_min_error_statement | debug1 | configuration file log_min_messages | debug1 | configuration file log_rotation_size | 1GB | configuration file log_temp_files | 0 | configuration file log_timezone | localtime | configuration file logging_collector | on | configuration file maintenance_work_mem | 3GB | configuration file max_connections | 10 | configuration file max_locks_per_transaction | 256 | configuration file max_parallel_workers_per_gather | 14 | configuration file max_stack_depth | 2MB | environment variable max_wal_size | 4GB | configuration file max_worker_processes | 14 | configuration file min_wal_size | 2GB | configuration file parallel_setup_cost | 1000 | configuration file parallel_tuple_cost | 0.012 | configuration file port | 5432 | configuration file random_page_cost | 22 | configuration file seq_page_cost | 1 | configuration file shared_buffers | 34GB | configuration file shared_preload_libraries | pg_stat_statements | configuration file ssl | on | configuration file ssl_cert_file | /etc/ssl/certs/ssl-cert-snakeoil.pem | configuration file ssl_key_file | /etc/ssl/private/ssl-cert-snakeoil.key | configuration file statement_timeout | 1000000s | configuration file stats_temp_directory | /var/run/postgresql/9.6-main.pg_stat_tmp | configuration file superuser_reserved_connections | 1 | configuration file syslog_facility | local1 | configuration file syslog_ident | postgres | configuration file syslog_sequence_numbers | on | configuration file temp_file_limit | 80GB | configuration file TimeZone | localtime | configuration file track_activities | on | configuration file track_counts | on | configuration file track_functions | all | configuration file unix_socket_directories | /var/run/postgresql | configuration file vacuum_cost_delay | 1ms | configuration file vacuum_cost_limit | 5000 | configuration file vacuum_cost_page_dirty | 200 | configuration file vacuum_cost_page_hit | 10 | configuration file vacuum_cost_page_miss | 100 | configuration file wal_buffers | 16MB | configuration file wal_compression | on | configuration file wal_sync_method | fdatasync | configuration file work_mem | 1468006kB | configuration file The part of /etc/sysctl.conf I modified is: vm.swappiness = 1 vm.dirty_background_bytes = 134217728 vm.dirty_bytes = 1073741824 vm.overcommit_ratio = 100 vm.zone_reclaim_mode = 0 kernel.numa_balancing = 0 kernel.sched_autogroup_enabled = 0 kernel.sched_migration_cost_ns = 5000000 The problem I have is very poor read. When I benchmark my array with fio I get random reads of about 200MB/s and 1100IOPS and sequential reads of about 286MB/s and 21000IPS. But when I watch my queries using pg_activity, I get at best 4MB/s. Also using dstat I can see that iowait time is at about 25%. This problem is not query-dependent. I backed up the database, I reformated the array making sure it is well aligned then restored the database and got the same result. Where should I target my troubleshooting at this stage? I reformatted my drive, I tuned my postgresql.conf and OS as much as I could. The hardware doesn’t seem to have any issues, I am really puzzled. Thanks! Charles -- Charles Nadeau Ph.D.
