On Dec 1, 2006, at 5:42 PM, Sean Murphy wrote:
Thank you for your knowledge on this issue. I have a few
questions that I need your help to clarify.
You are welcome, although knowledge can be a tricky thing. :-)
"Snapshots are taken via mksnap_ffs; some other tools like fsck or
dump also know how to create a snapshot."
OK, so if I understand this correctly I do not have to
initially take a snapshot and update this snapshot manually. The
files system with soft updates does it correct?
If the system is rebooted with a filesystem which is marked unclean,
and if soft updates is enabled, then yes, the background fsck process
will create a snapshot automatically, and not need manual intervention.
"Maybe. I think that softupdates is a win in almost all
circumstances from the standpoint of data consistency, short of
fully syncronous data & metadata updates."
On this issue, if I do not have soft updates on does that
make it a fully synchronous file system?
No. Take a look at the manpage for "mount", in particular the
section on -o which discusses async, sync, and noasync. The latter
is the default:
" noasync
Metadata I/O should be done synchronously,
while data I/O
should be done asynchronously. This is the
default."
If the background fsck can't handle the inconsistencies it will
report this in the /var/log/messages correct? Then is the file
system unmounted because of the inconsistency to prevent data loss,
so I can run a manual fsck or does it stay mounted?
It should fall back to running a foreground fsck instead, which might
indeed require manual intervention, I believe.
--
-Chuck
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