Software RAID issues (was Re: Suggestions solicited, server bring up)

[Ken D'Ambrosio]

>> I think the only other
>> filesystems that checksum are NetApp's WAFL(?) and Linux's btfrs.

No; check out Wikipedia's filesystem comparison page, below.  That being
said, ain't many, and most of them are new.

http://en.wikipedia.org/wiki/Comparison_of_file_systems#Metadata

> In an interesting blast from the past, MS-DOS FAT maintains a
> checksum.  IIRC, it's 32-bit CRC across the entire file, so it isn't very
> robust, but I've seen it successfully detect errors before.  So MS-DOS FAT
> actually has a feature Linux EXT3 lacks.  Whodathunkit?

UDNRC [sic].  With all due respect to the encyclopedic knowledge of Ben, I
took this one with a grain of salt.  And again, Wikipedia to the rescue:
long filename FAT had checksums for the *filename*, not the file data. 
This was to to ensure that the 8.3 filename matched the long filename.
http://en.wikipedia.org/wiki/File_Allocation_Table

> You can do this on Linux with LVM snapshots.

And, indeed, it may actually be implemented via btrfs in the next release
of Rawhide:
http://lwn.net/SubscriberLink/362500/8331dbd6172b5b85/

-Ken


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