WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

Re: [Xen-users] forcing disk in read only also if mounted

On Tuesday 16 January 2007 4:23 am, Daniele Palumbo wrote:
> but, which is the difference between that approach with "w!" (saying that
> all domU's will mount only ro) and the above?

"w!" tells to the Xen device handling not to check anything, in case you want 
to use a cluster FS (ocfs2 or GFS).  both "r" and "w" check that you're safe 
to use 'normal' filesystems.  a "r!" as you wish would allow one rw and 
several ro; something that is not supported by any non-cluster filesystem.

i think you beleive that somehow making an exception for Dom0, letting it 
write 'sometimes' is still 'almost safe'.  it is not.

> domU's will became unstable (strange, i figured out only files missing, as
> i think it should be) in the same way, and also (saying that i have "bad
> guys playing with my domUs) i can have a data loss.

all FS i know about (except maybe FAT, of course) might do complex and 
sophisticated things with the directory structures any time you write.  (some 
of them reshuffle file data too).  for example, ext3 keeps the directory 
sorted and changes from a linear list to an htree after a given threshold.

> so, again, why is not "r!" a valid flag?

because it doesn't make any sense.  "r" and "w" are 'safe', "w!" is safe too 
if you know what you're doing (cluster FS); "r!" as you wish wouldn't be safe 
for any non-cluster FS, and useless for cluster FSs

-- 
Javier

Attachment: pgpec4I0NAD5u.pgp
Description: PGP signature

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
<Prev in Thread] Current Thread [Next in Thread>