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+<body>
+<h1 align="center">
+Internal Versus External BLOBs in SQLite
+</h1>
+
+<p>
+If you have a database of large BLOBs, do you get better read performance
+when you store the complete
+BLOB content directly in the database or is it faster to store each BLOB
+in a separate file and store just the corresponding filename in the database?
+</p>
+
+<p>
+To try to answer this, we ran 49 test cases with various BLOB sizes and
+SQLite page sizes on a Linux workstation (Ubuntu circa 2011 with the
+Ext4 filesystem on a fast SATA disk).
+For each test case, a database was created containing 100MB of BLOB
+content.  The sizes of the BLOBs ranged from 10KB to 1MB.  The number
+of BLOBs varied in order to keep the total BLOB content at about 100MB.
+(Hence, 100 BLOBs for the 1MB size and 10000 BLOBs for the 10K size and
+so forth.)  SQLite <a href="releaselog/3_7_8.html">version 3.7.8</a> (2011-09-19) was used.
+</p>
+
+<blockquote><i>
+Update: New measurements for SQLite version 3.19.0
+(2017-05-22) show that SQLite is about 
+<a href="fasterthanfs.html">35% faster</a> than direct disk I/O for 
+both reads and writes of 10KB blobs.
+</i></blockquote>
+
+<p>
+The matrix below shows the time needed to read BLOBs stored in separate files
+divided by the time needed to read BLOBs stored entirely in the database.  
+Hence, for numbers larger than 1.0, it is faster to store the BLOBs directly 
+in the database.  For numbers smaller than 1.0, it is faster to store the BLOBs
+in separate files.
+</p>
+
+<p>
+In every case, the pager cache size was adjusted to keep the amount of
+cache memory at about 2MB.  
+For example, a 2000 page cache was used for 1024 byte pages
+and a 31 page cache was used for 65536 byte pages.
+The BLOB values were read in a random order.
+</p>
+
+<table border="1" cellpadding="5" cellspacing="0" align="center">
+<tr>
+<th rowspan="2">Database Page Size<th colspan="7">BLOB size
+<tr>
+<th>10k<th>20k<th>50k<th>100k<th>200k<th>500k<th>1m
+
+<tr>
+<td>1024<td bgcolor="#b1d3a8">1.535<td bgcolor="#b1d3a8">1.020<td bgcolor="#ffc0d0">0.608<td bgcolor="#ffc0d0">0.456<td bgcolor="#ffc0d0">0.330<td bgcolor="#ffc0d0">0.247<td bgcolor="#ffc0d0">0.233
+
+<tr>
+<td>2048<td bgcolor="#b1d3a8">2.004<td bgcolor="#b1d3a8">1.437<td bgcolor="#ffc0d0">0.870<td bgcolor="#ffc0d0">0.636<td bgcolor="#ffc0d0">0.483<td bgcolor="#ffc0d0">0.372<td bgcolor="#ffc0d0">0.340
+
+<tr>
+<td>4096<td bgcolor="#b1d3a8">2.261<td bgcolor="#b1d3a8">1.886<td bgcolor="#b1d3a8">1.173<td bgcolor="#ffc0d0">0.890<td bgcolor="#ffc0d0">0.701<td bgcolor="#ffc0d0">0.526<td bgcolor="#ffc0d0">0.487
+
+<tr>
+<td>8192<td bgcolor="#b1d3a8">2.240<td bgcolor="#b1d3a8">1.866<td bgcolor="#b1d3a8">1.334<td bgcolor="#b1d3a8">1.035<td bgcolor="#ffc0d0">0.830<td bgcolor="#ffc0d0">0.625<td bgcolor="#ffc0d0">0.720
+
+<tr>
+<td>16384<td bgcolor="#b1d3a8">2.439<td bgcolor="#b1d3a8">1.757<td bgcolor="#b1d3a8">1.292<td bgcolor="#b1d3a8">1.023<td bgcolor="#ffc0d0">0.829<td bgcolor="#ffc0d0">0.820<td bgcolor="#ffc0d0">0.598
+
+<tr>
+<td>32768<td bgcolor="#b1d3a8">1.878<td bgcolor="#b1d3a8">1.843<td bgcolor="#b1d3a8">1.296<td bgcolor="#ffc0d0">0.981<td bgcolor="#ffc0d0">0.976<td bgcolor="#ffc0d0">0.675<td bgcolor="#ffc0d0">0.613
+
+<tr>
+<td>65536<td bgcolor="#b1d3a8">1.256<td bgcolor="#b1d3a8">1.255<td bgcolor="#b1d3a8">1.339<td bgcolor="#ffc0d0">0.983<td bgcolor="#ffc0d0">0.769<td bgcolor="#ffc0d0">0.687<td bgcolor="#ffc0d0">0.609
+
+</table>
+
+
+<p>We deduce the following rules of thumb from the matrix above:</p>
+
+<ul>
+<li><p>
+A database page size of 8192 or 16384 gives the best performance
+for large BLOB I/O.
+
+<li><p>For BLOBs smaller than 100KB, reads are faster when
+the BLOBs are stored directly in the database file.  For BLOBs larger than
+100KB, reads from a separate file are faster.
+</ul>
+
+<p>Of course, your mileage may vary depending on hardware, filesystem,
+and operating system.  Double-check these figures on target hardware
+before committing to a particular design.
+<p align="center"><small><i>This page last modified on  <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink"  data-href="https://sqlite.org/docsrc/finfo/pages/intern-v-extern-blob.in?m=1022bf7228">2022-04-18 02:55:50</a> UTC </small></i></p>
+