[issue1984] hammer mount fails after crash - HAMMER: FIFO record bad head signature ..

["Thomas Nikolajsen \(via DragonFly issue tracker\)" <sinknull@xxxxxxxxxxxxxxxxxxxxx>]

Thomas Nikolajsen <thomas.nikolajsen@mail.dk> added the comment:

Thanks for the heads up on hw.physmen; I used fresh master, so its OK.
I haven't seen any further problems using the FS; no crashes either.

To enlarge UNDO/REDO FIFO on FS I need to newfs_hammer FS, right?
(of cause backup data before newfs_hammer ;-)

If I understand, UNDO/REDO FIFO is only in first volume,
also called root volume, in HAMMER FS, right?

If so, it could be an idea to ask user for planned size of FS
when doing newfs_hammer (new option);
he might use a small root volume (e.g. 50GB), and later add some big volumes.

Is UNDO/REDO FIFO of 0.1% total FS size recommended for a big HAMMER FS,
or how large should it be depending on FS size and RAM size?
(maybe size also depends on I/O bandwidth of disk subsystem, if e.g.
a given number of seconds worth of disk I/O should be in UNDO/REDO FIFO)

Do you plan changes to HAMMER FS / VFS for things like this issue?

 -thomas

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