Re: Is there a way to keep the 2.6 kjournald from writing to idle disks? (to allow spin-downs)

[Lutz Vieweg <lkv@isg.de>]

Felipe Alfaro Solana wrote:
> On Sun, 2004-01-25 at 19:29, Lutz Vieweg wrote:
>
>>I run a server that usually doesn't have to do anything on the local filesystems,
>>it just needs to answer some requests and perform some computations in RAM.
>>
>>So I use the "hdparm -S 123" parameter setting to keep the (IDE) system disk from
>>spinning unneccessarily.
>>
>>Alas, since an upgrade to kernel 2.6 and ext3 filesystem, I cannot find a way to
>>let the harddisk spin down - I found out that "kjournald" writes a few blocks every
>>few seconds.
>>
>>As I wouldn't like to downgrade to ext2: Is there any way to keep the 2.6 kjournald
>>from writing to idle disks?
>>
>>I cannot see a good reason why kjournald would write when there are no dirty buffers -
>>but still it does.
> 
> 
> Have you tried playing with the laptop-mode patch? It's already in the
> -mm kernel tree from Andrew Morton. I've been playing with it a little
> (just a few minutes) and seems keep the disks spun down for some time.

This "laptop-mode" patch would make things far worse than they're now: Spinning
up the disk about every 10min would reduce their lifetime significantly instead
of extending it.

It's not a laptop, but a server with an ordinary 3.5" harddisk I'm speaking about,
my goal is not saving power, but spinning down a harddisk that does not need to
spin up the whole day long.

What I'm questioning is whether there's a need to write to idle disks at all -
does anybody know why kjournald writes data even if there is nothing to commit at all?

Regards,

Lutz Vieweg