Talk:Dataset: Difference between revisions
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migrate>Ma-F Created page with "what does mean those deduplication options: <span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">ON, </span><span style="color: ..." |
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what does mean those deduplication options: <span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">ON, </span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">VERIFY,</span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;"> SHA256, </span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">SHA256 VERIFY ???</span> | what does mean those deduplication options: <span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">ON, </span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">VERIFY,</span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;"> SHA256, </span><span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;">SHA256 VERIFY ???</span> | ||
<span style="color: rgb(0, 0, 0); font-family: undefined, sans-serif; font-size: 12.8px;"></span><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">If you accept the mathematical claim that a secure hash like SHA256 has</span> | |||
<span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">only a 2\^-256 probability of producing the same output given two different</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">inputs, then it is reasonable to assume that when two blocks have the</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">same checksum, they are in fact the same block. You can trust the hash.</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">An enormous amount of the world's commerce operates on this assumption,</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">including your daily credit card transactions. However, if this makes</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">you uneasy, that's OK: ZFS provies a 'verify' option that performs</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">a full comparison of every incoming block with any alleged duplicate to</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">ensure that they really are the same, and ZFS resolves the conflict if not.</span><br/><span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;">To enable this variant of dedup, just specify 'verify' instead of 'on':</span> | |||
<span style="color: rgb(64, 64, 64); font-family: Arial, Helvetica, sans-serif; font-size: 18px;"></span>https://blogs.oracle.com/bonwick/zfs-deduplication-v2 | |||
Latest revision as of 10:27, 6 February 2018
what does mean those deduplication options: ON, VERIFY, SHA256, SHA256 VERIFY ???
If you accept the mathematical claim that a secure hash like SHA256 has
only a 2\^-256 probability of producing the same output given two different
inputs, then it is reasonable to assume that when two blocks have the
same checksum, they are in fact the same block. You can trust the hash.
An enormous amount of the world's commerce operates on this assumption,
including your daily credit card transactions. However, if this makes
you uneasy, that's OK: ZFS provies a 'verify' option that performs
a full comparison of every incoming block with any alleged duplicate to
ensure that they really are the same, and ZFS resolves the conflict if not.
To enable this variant of dedup, just specify 'verify' instead of 'on':