From: | "t(dot)dalpozzo(at)gmail(dot)com" <t(dot)dalpozzo(at)gmail(dot)com> |
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To: | pgus-general(at)postgresql(dot)org |
Subject: | journaled FS and and WAL |
Date: | 2016-10-14 11:22:55 |
Message-ID: | 5800C00F.4030208@gmail.com |
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Thread: | |
Lists: | pgus-general |
Hi,
two question related to the WAL.
1) I read in the doc that journaled FS is not important as WAL is
journaling itself. But who garantees that the WAL is written correctly?
I know that it's sequential and a partial update of WAL can be discarded
after a restart. But am I sure that without a journaled FS, if there is
a crash during the WAL update, nothing already updated in the WAL before
my commit can get corrupted?
2) Let's suppose that I have one database, one table of 100000 rows,
each 256 bytes. Now, in a single SQL commit, I update row 10, row 30000
and row 80000. How much should I expect the WAL increase by? (supposing
no WAL segments will be deleted). I could guess 8192x3 but I'm not sure
Regards
Pupillo
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