diff --git a/doc/paper3/LLADD.tex b/doc/paper3/LLADD.tex index 1864b03..1bf63a0 100644 --- a/doc/paper3/LLADD.tex +++ b/doc/paper3/LLADD.tex @@ -975,12 +975,12 @@ logically consistent. \begin{figure} \includegraphics[% - viewport=0bp 0bp 445bp 365bp, + viewport=0bp 0bp 445bp 308bp, clip, width=1\columnwidth]{figs/torn-page.pdf} \caption{\sf\label{fig:torn}Torn pages and LSN-free recovery. The page is torn during the crash, but consistent once redo completes. -Overwritten and stale torn sectors are shaded.} +Overwritten sectors are shaded.} \end{figure} \rcs{Next 3 paragraphs are new; check flow, etc} @@ -990,17 +990,17 @@ of writing out the version with LSN $2$ when the system crashes. When recovery reads the page from disk, it may encounter any combination of sectors from these two versions. -Note that the first and last two sectors are not overwritten by any of +Note that sectors zero, six and seven are not overwritten by any of the log entries that Redo will play back. Therefore, their values are -unchanged in both versions of the page. In the example, two of these -sectors are overwritten during the crash, while the shaded one is left -over from the old version of the page. +unchanged in both versions of the page. In the example, zero and seven +are overwritten during the crash, while six is left +over from the old version of the page. Redoing LSN 1 is unnecessary, since all of its sectors happened to make it to disk. However, recovery has no way of knowing this and -applies the entry to the page, replacing a up-to-date sector with a -stale one. When LSN 2 is applied, it brings this sector up to date, -and also overwrites one of the two sectors that did not make it to +applies the entry to the page, replacing sector three with an older +version. When LSN 2 is applied, it brings this sector up to date, +and also overwrites sector four, which did not make it to disk. At this point, the page is internally consistent. Since LSN-free recovery only relies upon atomic updates at the bit diff --git a/doc/paper3/figs/torn-page.pdf b/doc/paper3/figs/torn-page.pdf index a955dd6..243e679 100755 Binary files a/doc/paper3/figs/torn-page.pdf and b/doc/paper3/figs/torn-page.pdf differ