On 1/28/2010 6:51 PM, Adam Vande More wrote:
On Thu, Jan 28, 2010 at 10:42 AM, Nikos Vassiliadis<nvass9...@gmx.com>wrote:
Hi,
I am using a 40MB journal on a 500MB compact flash.
Would that be sane, or I am causing more harm than
good?
My concerns are:
1) wear leveling. The journal is on specific part
of the "disk" writing again and again. That
should be handled by the CF itself. Though
I am not sure it does a good job???
2) I do care about ungraceful power cycles and I've seen
posts on the net, mentioning:
More, If
you interrupt power at arbitrary times while the device is writing,
you can lose the integrity of the file system being modified. The loss
is not limited to the 512 byte sector being modified, as it generally
is with rotating disks; you can lose an entire erase block, maybe 64K
at once.
I guess the above comment renders the use
of a journaling filesystem useless. But, doing
some naive tests, power cycling the machine
while writing and checksumming the data after
fsck in preen mode, revealed no error.
Thanks in advance for any insights, Nikos
Soft Updates seem more appropriate for a 500MB CF drive than gjournal.
AFAIK, they are a wash in terms of reliability, and gjournal needs to write
all data twice meaning it's slower, and increases the wear on the drive.
The big drawback to soft updates is the fsck times after an unclean shutdown
which really shouldn't be an issue on a 500MB drive.
fsck time in my case is not an issue. What concerns me mostly is
a situation where user intervention is required. The CF filesystem
will be used in a embedded system and should work without user
intervention. I too feel that geom journaling is not the best
solution for my needs, but softupdates need more attention than
gjournal. Perhaps, I should wait for SUJ, which will be in the
tree soon.
Nikos
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