On Sat, 18 Aug 2001 at 12:34, Juan Miguel Cacho wrote:
> Now that I'm using reiserfs can I do away with my poor man's UPS?
> (* * * * * root /bin/sync in crontab)
> Or should I just leave it there, anyway it does no harm?
ReiserFS caches much more aggressively than ext2, so there's still a need
for something similar to your "poor man's UPS".
There was this discussion in the XFS list that didn't quite end
conclusively. But anyway, I did a little research on bdflush and proposed
that instead of running sync every second, why not update bdflush to sync
every 1 second instead of every 30, as is the default?
Note the following:
jijo@gusi:~$ cat /proc/sys/vm/bdflush
30 64 64 256 500 3000 60 0 0
These are the defaults. The 6th and 7th entries are explained as follows
(from /usr/src/linux/Documentation/filesystems/proc.txt):
age_buffer Time for normal buffer to age before we flush it
age_super Time for superblock to age before we flush it
And more elaborately:
age_buffer and age_super
------------------------
Finally, the age_buffer and age_super parameters govern the maximum time
Linux waits before writing out a dirty buffer to disk. The value is
expressed in jiffies (clockticks), the number of jiffies per second is
100. Age_buffer is the maximum age for data blocks, while age_super is
for filesystems meta data.
So setting age_buffer to 100 jiffies (one second), the system should
_theoretically_ flush normal buffers to disk every second. This can be
done by:
jijo@gusi:~$ echo "30 64 64 256 500 100 60 0 0" > /proc/sys/vm/bdflush
Note that by experience I've found that age_buffer cannot be < 100. It
just won't accept it.
--> Jijo
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