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--- freebsd:zfs [2020/10/20 06:47] – sleepy
+++ freebsd:zfs [2025/07/07 23:10] (current) – external edit 127.0.0.1
@@ Line 2: / Line 2: @@
 <code>zfs list</code> shows USED and AVAILABLE after parity/redundancy are removed
 <code>zpool list</code> shows ALLOCATED and FREE including space occupied by parity/redundancy
+----
 ====== Create ZFS dataset ======
 ===== PostgreSQL =====
+~~REFNOTES~~
+==== notes ====
+  * use ZFS's cache is postgresql dataset exceeds RAM, use postgres's cache if dataset fits in RAM
+    * disable postgres cache, enable ZFS cache
+    * enable postgres cache, disable ZFS cache
 ==== zfs ====
   * **atime=off** -- disable access time recording for files when they are read
   * **compression=lz4** -- turn on compression
   * **recordsize=8k** -- set record size to postgres's default write block size 8k
-  * **logbias=throughput**
+  * **logbias=throughput**  --
-  * **primarycache=metadata** -- ARC only cache metadata (dnode entries), not page data itself
+  * **primarycache=metadata** -- ARC only cache metadata (dnode entries), not page data itself. DO NOT disable if PostgreSQL's cache is disabled!
   * quota=500G
@@ Line 19: / Line 23: @@
   * disable full_page_writes
   * disable PostgreSQL TOAST compression
+  * dedicate 15%-25% physical ram to ARC, and 50% to shared_buffers
+=== raw benchmark data ===
+{{tablelayout?tableSort=1}}
+^ pgbench -c 10 -j 2 -t 10000 ^ inc. connections est. ^ exc. connections est. ^ latency ^
+| BASE |  6775 |  6776 |  1.476 ms |
+| primarycache=metadata |  3850 |  3850 |  2.597 ms |
+| primarycache=metadata compression=lz4 |  4815 |  4816 |  2.077 ms |
+| primarycache=metadata compression=lz4 recordsize=16k |  4160 |  4160 |  2.404 ms |
+| primarycache=metadata, compression=lz4, recordsize=16k, atime=off |  3415 |  3415 |  2.928 ms |
+| primarycache=metadata, compression=lz4, recordsize=8k, atime=off |  4362 |  4363 |  2.292 ms |
+| primarycache=metadata, compression=lz4, recordsize=8k, atime=off, \\ shared_buffers=2048MB |  5862 |  5863 |  1.706 ms |
+| primarycache=metadata, compression=lz4, recordsize=16k, atime=off, \\ shared_buffers=2048MB |  5819 |  5820 |  1.718 ms |
+| compression=lz4, recordsize=16k, atime=off, \\ shared_buffers=2048MB |  7628 |  7628 |  1.311 ms |
+| compression=lz4, recordsize=16k, atime=off, \\ shared_buffers=4096MB |  7332 |  7333 |  1.364 ms |
+| compression=lz4, recordsize=16k, atime=off, logbias=throughput, \\ shared_buffers=4096MB, synchronous_commit=off |  27052 |   27067 |  0.370 ms |
+| compression=lz4, recordsize=16k, atime=off, logbias=throughput, \\ shared_buffers=4096MB, synchronous_commit=off, full_page_writes=off |  30348 |  30366 |  0.330 ms |
+----
 ====== /boot/loader.conf ======
 <code>
@@ Line 64: / Line 84: @@
 </code>
+----
 ===== Benchmarks =====
 {{tablelayout?tableSort=1}}