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3 | 3 | <chapter id="wal"> |
4 | 4 | <title>Reliability and the Write-Ahead Log</title> |
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59 | 59 | same concerns about data loss exist for write-back drive caches as |
60 | 60 | exist for disk controller caches. Consumer-grade IDE and SATA drives are |
61 | 61 | particularly likely to have write-back caches that will not survive a |
62 | | - power failure. Many solid-state drives also have volatile write-back |
63 | | - caches. To check write caching on <productname>Linux</> use |
| 62 | + power failure, though <acronym>ATAPI-6</> introduced a drive cache |
| 63 | + flush command that some file systems use, e.g. <acronym>ZFS</>. |
| 64 | + Many solid-state drives also have volatile write-back |
| 65 | + caches, and many do not honor cache flush commands by default. |
| 66 | + To check write caching on <productname>Linux</> use |
64 | 67 | <command>hdparm -I</>; it is enabled if there is a <literal>*</> next |
65 | 68 | to <literal>Write cache</>; <command>hdparm -W</> to turn off |
66 | 69 | write caching. On <productname>FreeBSD</> use |
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