8 Contributors: |
8 Contributors: |
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10 <!DOCTYPE concept |
10 <!DOCTYPE concept |
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12 <concept id="GUID-3FEEFC4D-19B5-502A-8310-40646B9C34BC" xml:lang="en"><title>Run |
12 <concept id="GUID-3FEEFC4D-19B5-502A-8310-40646B9C34BC" xml:lang="en"><title>Run |
13 time cache settings</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
13 time cache settings</title><shortdesc>This topic describes the rum time cache settings.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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16 <p><b>Read caching </b> </p> |
16 <p><b>Read caching </b> </p> |
17 <p>A client, or multiple clients, may issue repeated requests to read data |
17 <p>A client, or multiple clients, may issue repeated requests to read data |
18 from the same locality within a file. Data that has been read previously that |
18 from the same locality within a file. Data that has been read previously that |
19 is still in the cache can be returned to the client without continuously re-reading |
19 is still in the cache can be returned to the client without continuously re-reading |
20 the data from the media. </p> |
20 the data from the media. <note>Read caching has little benefit when files |
21 <p> <b>Note</b>: Read caching has little benefit when files are accessed sequentially |
21 are accessed sequentially in large blocks, and are never re-read. </note> </p> |
22 in large blocks, and are never re-read. </p> |
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23 |
22 |
24 |
23 |
25 <p><b>Read ahead caching </b> </p> |
24 <p><b>Read ahead caching </b> </p> |
26 <p>Read ahead caching builds on read caching by detecting clients that are |
25 <p>Read ahead caching builds on read caching by detecting clients that are |
27 performing streaming operations and speculatively reading ahead on the assumption |
26 performing streaming operations and speculatively reading ahead on the assumption |
32 <p><b>Write caching </b> </p> |
31 <p><b>Write caching </b> </p> |
33 <p>Write caching is implemented to perform a small level of write back caching |
32 <p>Write caching is implemented to perform a small level of write back caching |
34 that overcomes the inefficiencies of clients that perform small write operations |
33 that overcomes the inefficiencies of clients that perform small write operations |
35 by consolidating multiple file updates into a single larger write operation, |
34 by consolidating multiple file updates into a single larger write operation, |
36 thus taking advantage of media that is written on a block basis as well as |
35 thus taking advantage of media that is written on a block basis as well as |
37 minimising the overhead of metadata updates that the file system performs. </p> |
36 minimizing the overhead of metadata updates that the file system |
38 <section><title>Opening files with different modes</title> <p>The system is |
37 performs. </p> |
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38 <section id="GUID-8653BC99-0FA6-4FA0-AEBD-066C0BE91B57"><title>Opening files with different modes</title> <p>The system is |
39 configured by partners. Read caching, read ahead caching and write caching |
39 configured by partners. Read caching, read ahead caching and write caching |
40 are set on a per drive basis and are one of three states, these are:</p><ul> |
40 are set on a per drive basis and are one of three states, these are:</p><ul> |
41 <li><p>ON </p></li> |
41 <li><p>ON </p></li> |
42 <li><p>ENABLED </p></li> |
42 <li><p>ENABLED </p></li> |
43 <li><p>OFF</p></li> |
43 <li><p>OFF</p></li> |