| title: | Re a few questions about ext3 journal |
|
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JÃrÃme Petazzoni wrote:
A few wild ideas/questions :
1) Is there a way to check the size of the journal of an ext3 filesystem ?
I mean - the actually used size ; not the total size of the journal.
perhaps "logdump -ac" (within debugfs) will help - i you can tell from its
output what parts are "used".
2) Would it be difficult to implement "freeze" of ext3 filesystem - that
is, blocking all I/O to the filesystem until its "unfrozen" (XFS can do
that), for two purposes :
A/ allowing "freezing" in a clean state, to allow clean snapshotting
would "remount,ro" be sufficient?
B/ allowing "freezing" while moving a SCSI disk or a network-connected
disk without umounting filesystem
err, "unplug the cable without unmounting the filesystem"?? youd have to
hold the entire fs in ram for the "move" or i dont understand what you mean.
3) Is it possible to allow data to stay in the journal for a very long
time ?
Rationale : for laptops with a lot of memory and some solid-state
memory, this would allow to shutdown the hard disk (if all read data is
in the cache, and all written data goes to the log on the solid-state
disk).
the only tuneable which comes to my mind right now is the "commit"
paramater for mount:
commit=nrsec
Sync all data and metadata every nrsec seconds. The default value
is 5 seconds. Zero means default.
and there are the laptop-mode-tools [1] using some kernel hacks to spin
down disks and continue working.
Christian.
[1] www.xs4all.nl/~bsamwel/laptop_mode/ www.xs4all.nl/~bsamwel/laptop_mode/
- --
BOFH excuse #375:
Root name servers corrupted.
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