[nylug-talk] Re :Re: extfs journalling percentage (Chris Knadle)

[Michael Bubb]

> From: Chris Knadle <Chris.Knadle at coredump.us>
> To: NYLUG Technical Discussion <nylug-talk at nylug.org>
> Date: Tue, 27 May 2008 11:41:55 -0400
> Subject: Re: [nylug-talk] extfs journalling percentage
> On Tuesday 27 May 2008, Michael Bubb wrote:
>> Taking home as an example the actual numbers are:
>> /dev/sda6             72437948  49776256  18982008  73% /home
>>
>> The file system in this case is ext3.
>> On this and other similar servers in my company, I have noticed a 5.1%
>> 'overhead' on the difference between the partition's capacity and its
>> amount usable.
>> I realize this is the journal and the blocks reserved for root.
>>
>> Looking at the man page for mkfs.ext3 I see that there is a '-m' flag
>> which can adjust this. Do you have recommendations for this? I do not
>> know much about filesystems and tend to leave the default settings
>> alone...
>>
>> If I understand correctly the actual journal is not that big. Most of
>> this 5% is reserved so that a superuser has access to  an otherwise
>> full partition. Do you need 5% for this? (ie if you have a 250G
>> parttion do you need 13G reserved).
>>
>> Thanks as always
>>
>> Michael
>
>   I'm not 100% positive, but I don't think the ext3 journal counts in that 5%
> reserved for root-only usage.  Mainly I think that this is space set aside
> for root for having a place to do emergency filesystem repair, like using
> debugfs or similar utilities.  I've often wondered the same thing you have
> and on occasion I've set up a test box with 0% reserved space and nothing
> terrible happened, but then again I also didn't have a problem such that I'd
> need a space to work with debugfs, etc.
>   i.e. I believe whether you need it or not is a question of your own
> administration needs rather than the filesystem's own requirements.
>
>   -- Chris
>
> --
>
> Chris Knadle
> Chris.Knadle at coredump.us
>
>
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Thank you Chris.
Now I am intruiged as to how to use this admin space in an actual
crash.  Guess I will try and google more on the purpose for this.

-- 
Michael Bubb | Hoboken, NJ | 201.736.0870

"Just because Richard Stallman is paranoid doesn't mean Microsoft's
not out to get you. " - (theodc on slashdot)