Re: Advice about ext3, please
On 2009-03-09_09:20:06, Steven Demetrius wrote:
> Paul E Condon wrote:
>> On 2009-03-08_13:41:53, Lists wrote:
>>> Steven Demetrius wrote:
>>>> Paul E Condon wrote:
>>>>> I'd like some confirmation, or refutation, of some reasoning:
>>>>>
>>>>> I have a USB external hard drive. It came with vfat fs, but I want to
>>>>> write an ext2/3 fs on it. All my internal HD are ext3, but should this
>>>>> one be ext3, also? Doesn't ext3 essentially write everything twice,
>>>>> first to the journal, and then to the actual target location? This is
>>>>> OK with an internal bus interface from the CPU to the HD, but USB is
>>>>> not so fast. So I think I should not use ext3 for this HD. Is this
>>>>> correct?
>>>>>
>>>>> TIA
>>>> Basically ext3 is ext2 with Journaling. Journaling basically
>>>> safe-guards against power failure and system crashes. It is well
>>>> suited for system partitions and partitions that are being used
>>>> most of the time your computer is on.
>>>>
>>>> Journaling uses significantly more disk space and does not allow for
>>>> deleted file recovery. IT uses more resources that ext2. Journaling
>>>> does not write everything twice. It keeps track of the file system
>>>> which makes recovery fast and more reliable than file systems
>>>> without Journaling.
>>>>
>>>> I recommend the following:
>>>>
>>>> ext3 - for system partitions and data partitions which are in use
>>>> most of the time (/, /home, /var, etc. if they are separate
>>>> partitions or drives).
>>>>
>>>> ext2 - for backup, removable, partitions rarely used, etc.
>>>>
>>>> If your USB external is for backup or file transfers then I
>>>> recommend using the ext2 file system on it. Logic being that if
>>>> your USB external data gets corrupted then you still have a copy of
>>>> the data on another partition.
>>>>
>>>> FYI:
>>>> Some people confuse backup with archiving. They will make copies of
>>>> their data and store it away until they have data problems with the
>>>> system. This is archiving.
>>>> Backup is a never ending routine whether done once a week or one a
>>>> month and also include regular data integrity checks of the backups.
>>>>
>>>>
>>> Correction:
>>> Journaling file system does write data twice.
>>> ttp://en.wikipedia.org/wiki/Ext3
>>
>> This is an interesting reference. I think I am convinced that journaling
>> in Linux is -not- a finished story.
>>
>> Thanks for pointing it out.
>>
>
> Paul:
>
> Did you take a look at the ext4 file system?
>
> Looking very interesting. Especially deframentation.
I read the description in wikipedia. We will all be doing ext4 in near
future, I think. But for now, my project is making an archive of my
check points. For this application I think ext2 provides a tiny decrease
in overhead, for an infinitessimal increase in unreliability. For this
app., there is always the option of a total re-run of any single job.
Other issues like USB 2.0 vs USB 1.1 loom -much- larger.
--
Paul E Condon
pecondon@mesanetworks.net
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