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Re: Maria-db refuses to start


the next reply-all clown.... boy i am subsribed so you can just respond to the list

Am 08.12.22 um 21:13 schrieb Gordan Bobic:
On Thu, Dec 8, 2022 at 9:42 PM Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote:

Am 08.12.22 um 18:59 schrieb Gordan Bobic:
On Thu, Dec 8, 2022 at 7:28 PM Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote:
MariaDB does the same as the filesystem
InnoDB in fact is more ore less a FS on top of a FS

So why do it at both levels?

because the FS layer can't detect MariaDB errors?

What is the net benefit of detecting said error? The way I see it, the
options are:
1) MariaDB detects and error, crashes out
2) MariaDB doesn't detect an error, ingests garbage, crashes out

silent data corruption

The only way an error will creep in without the error checking FS
spotting it is:
1) manually corrupting the block by writing garbage over it
2) MariaDB generated a duff block and wrote it out
3) Some other hardware failure corrupted the block in MariaDB memory,
just before writing it to the file system

If any of the latter set happens, the data is toast anyway.
If the former set happens, the data is toast anyway.

silent data corruption

Sure it's nice to get an error that confirms that your data is
corrupted, but that won't bring it back
silent data corruption

Shift it down to a layer where at least a subset of the problemspace
can be fixed and we have a net gain in at least some cases.

different world

And what makes doing it at MariaDB level
in any way better than doing it somewhere else?

which magic should do it somewehre else?

If a file system is in control of data mirroring and checksumming
every 16KB block, then if the data is corrupted on disk, file system
will detect it on a read and fetch a good copy from an uncorrupted

moron the files are fine from the viewpoint of the filessystem

Application never knows something went wrong, file system replaces the
corrupted block on the other disk and everything carries on

moron the files are fine from the viewpoint of the filessystem


So your argument is that the page checksum is there to tell you that
your data is corrupted because of either:
1) data was corrupted by the database itself, or
2) a superuser overwriting the block on the disk

and it's impressive how long it takes until you mororn understand such basics

In either case, you are not getting the data back either way the the
database will stop working.

yes, but it's a difference if you have silent data corruption detectet months later when clean backups are gone because retention times

So what is the point? I'd rather have the error fixable

moron your filesystem can't fix that type of error

that's why "Some of us run MariaDB on file systems that do their own block checksumming, and thus run innodb_checksum_algorithm=none" was an idiots response

a different response would have been "i don't think that i need innodb checksums and want to disable it" but you moron pretended your filesystem does the same

than have the
knowledge that I have an error I can do nothing about

moron your filesystem can't fix that type of error and you won't be aware that you have a problem not matter what FS you are using

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