gjournal on compact flash

Adam Vande More amvandemore at gmail.com
Thu Jan 28 16:51:25 UTC 2010

On Thu, Jan 28, 2010 at 10:42 AM, Nikos Vassiliadis <nvass9573 at 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.

Adam Vande More

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