Hi Ted,
For what it's worth, we have several petabytes of data residing in
ext3 file systems, a large staff of mainly non-idiots, and HA s/w,
and I still feel strongly that multi-mount protection is a good idea.
People, software, and hardware all malfunction in myriad ways, and the
more you have, the greater the odds (or so it seems to us). This
relatively simple safeguard at the fs level has high value IMHO.
Regards,
Jim
On Fri, 25 May 2007, Theodore Tso wrote:
Hi Kalpak,
On Tue, May 22, 2007 at 01:22:32AM +0530, Kalpak Shah wrote:
It will also protect against running e2fsck on a mounted filesystem
by adding similar logic to ext2fs_open().
Your patch didn't add this logic to ext2fs_open(); it just reserved
the space in the superblock.
I don't mind reserving the space so we don't have to worry about
conflicting superblock uses, but I'm still on the fence about actually
adding this functionality (a) into e2fsprogs, and (b) into the ext4
kernel code. I guess it depends on how complicated/icky the
implementation code is, I guess. The question as before is whether
the complexity is worth it, given that someone who is actually going
to be subject to accidentally mounting an ext3/4 filesystem on
multiple systems needs to be using an HA system anyway. So basically
this is just to protect against (a) a bug/failure in the HA subsystem,
and (b) the idiotic user that failed to realized he/she needed to set
up an HA subsystem in the first place. Granted, the universe is going
to create idiots at a faster rate that we can deal with it, but that's
why I'm still not 100% convinced the complexity is worth it.
To be fair, if I was on a L3 support team having to deal with these
idiots, I'd probably feel differently. :-)
- Ted
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