Subject RE: [IB-Architect] Disk data integrity (was: Torn Page detection)
Author Leyne, Sean

-----Original Message-----
From: Charlie Caro [mailto:ccaro@...]

I guess I qualify as "other than Ann".

Your credentials are impeccable!

I suggested to Ann duplicating the page generation field at the end of
page to detect page tears (mentioned in an earlier post by someone else)
as a minimal, cheap detection mechanism.

Seems quite reasonable and logical

I assume that you know the
maximum page size is 8KB, and not 16KB, but let's entertain the larger
page sizes because it's perfectly within the realm of future ODS

I did know that, it must have slipped my mind, I must have been thinking
about IB v8.0 <grin>


BTW, even if checksum capability was re-enabled, I would argue with a
default of inactivated checksums. The performance is just too great and
the occurrence of checksum errors too infrequent to justify as the
default. It's just not worth eliminating the checksum from the ODS for 2
bytes/page especially if you ever wanted to use it again. Then you would
have to wait years for the next ODS change.

I agree that the extra 2 bytes per page is not an unreasonable overhead
for a valuable feature. The checksum activation should be a switch
setting (at the DB level ???), but there was a post which suggested that
there are other checksum approaches which are not as expensive.