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: 600508B1001037383941424344450A
00 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.
Although probably not the root cause, at the least I would set up hugepages ( https://www.postgresql.org/docs/9.6/static/kernel-resources.html#LINUX-HUGE-PAGES ), and bump effective_io_concurrency up quite a bit as well (256 ?).
On Mon, Jul 10, 2017 at 10:03 AM, Charles Nadeau <charles.nadeau@xxxxxxxxx> wrote:
