Date: Tue, 14 Jun 2011 17:12:05 +0200 From: Per von Zweigbergk <pvz@itassistans.se> To: jhell <jhell@DataIX.net> Cc: freebsd-fs@freebsd.org Subject: Re: Disk usage and ZFS deduplication Message-ID: <61335943-0172-4483-A221-5C77CD8BAEFB@itassistans.se> In-Reply-To: <20110614150613.GB27199@DataIX.net> References: <9544F7B9-E286-4266-86E3-B4D1A667CBBD@itassistans.se> <20110614150613.GB27199@DataIX.net>
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14 jun 2011 kl. 17.06 skrev jhell: >=20 >=20 >=20 > On Tue, Jun 14, 2011 at 09:19:32AM +0200, Per von Zweigbergk wrote: >> I've been following the "Impossible compression ratio on ZFS" thread = with some interest, and it made me ask myself this: >>=20 >> Let us say we have a hypothetical zfs filesystem with the equally = hypothetical files A and B. The filesystem has deduplication enabled. = Both files have an apparent file size of 100 MB, but 50 MB of that data = is common between the two files and thus can be deduplicated. This would = mean that total disk usage would be 150 MB. >>=20 >> If you use "du" to determine disk size for a deduplication, what = would be the result? Which file would the common data be accounted to? = Or would it be accounted to both files somehow, in part or in full? >=20 > Logical answer would be that both files should be showing thier > resulting size regardless of how ZFS processes them. Being deduped = does > not mean representing files to the user any different. That would be the file size, yes, as opposed to the disk usage.=
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