Re: [LAU] Best file system for audio?

On Tue, Jun 28, 2011 at 9:07 PM, Gabriel M. Beddingfield
<gabrbedd@email-addr-hidden> wrote:
> On Tuesday, June 28, 2011 06:49:24 pm Christopher Cherrett
> wrote:
>> >   - For hard disk recording... use a NON-journaling
>> >
>> >     file system like ext2.  (E.g. mounted as
>> >     /tmp or something.)  This removes the overhead
>> >     of updating the journal for each transaction
>> >     to the disk.  If you have a power failure during
>> >     a recording, you're pretty fsck'd no matter which
>> >     way you go... so the journal won't help you.
>>
>> What type of performance hit does journalized file
>> systems take?
>>
>
> Here's the simplified concept of a journaling file system.
> For each chunk of data that will be written to the disk, the
> procedure is something like:
>
>  1. Add a log entry in the journal that you are going
>     to replace data at location A with data at
>     location B.
>
>  2. Write the data for location B.
>
>  3. Point the file system to location B instead of A.
>
>  4. Delete the log entry from the journal.

That is not how it is (usually) implemented.

> While this generally happens pretty fast... chances are that
> the journal, location A, and location B are in 3 totally
> different locations.  That means that the your disk will
> seek each time.  This lowers your throughput/bandwidth.

A good journalled file system should perform at least as well. The log
is written sequentially and the data pages usually need not be written
synchronously.

There are many huge variables, of course. Writing the log to a
different device can help a lot. Etc. etc.

> When recording (i.e. large, sequential files) on a non-
> journaling file system... you simply do step 2.  Over and
> over.  And you don't have to seek.  This improves your write
> performance.  But since you're not journaling, an unexpected
> power outage can result in a total filesystem corruption
> (but it's usually just a localized filesystem corruption).
>
> With that said, I've never had a problem recording on a
> journaling filesystem... but the original question was "what
> is the best?"
>
>> Does a non-journalized file system give you less latency?
>
> No.  It give you more hard drive bandwidth and more CPU
> headroom.
>
> Your hard disk performance has nothing to do with audio
> latency.

The only way to really answer any of these questions is with realistic
benchmark comparisons (not easy to do well).

-- 
 joq
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/listinfo/linux-audio-user