Re: Bobtail vs Argonaut Performance Preview

[Mark Nelson <mark.nelson@inktank.com>]

On 12/22/2012 12:45 PM, Christoph Hellwig wrote:
> On Sat, Dec 22, 2012 at 07:36:41AM -0600, Mark Nelson wrote:
>> Btw Christoph, thank you for taking the time to read my article.  If
>> I've done anything dumb or suboptimal regarding xfs, please do let
>> me know.  Soon I will be doing parametric sweeps over ceph parameter
>> spaces to see how performance varies on different hardware
>> configurations.  I want to make sure the tests are setup as
>> optimally as possible.
>
> You're defintively missing the "inode64" mount option, which we've
> always recommended, and which finally made it to be the default in
> Linux 3.7.
>

Is inode64 typically faster than inode32?  I thought I remembered 
dchinner saying that the situation wasn't always particularly clear and 
it depended on the workload.  Having said that, I can't really see it 
not being a good thing for Ceph to spread metadata out over all of the 
AGs, especially in the multi-disk raid config.  I'll use it for the next 
set of tests.

> Some other things worth playing with, but which aren't guaranteed to
> be a win are:
>
>   - use a larger than default log size (e.g. mkfs.xfs -l size=2g)
>   - use large directory blocks, similar to what you already do for btrfs
>     (mkfs.xfs -n size=16k or 64k)

I'll definitely give them a try at some point.  Thanks for the tips 
Christoph!

>
> Also at least for the benchmarks doing concurrent I/O (or any real life
> setup) you're probably much better off with a concatenation than a RAID 0
> for the multiple disk setup.
>