We have a 2TB HDD which we formated using default options of mkfs.ext4(v1.42.6).
I took around ~15 seconds to complete this operation.
Than we formatted the same partition with "-G 1024" and there was
around 30% performance improvement in
the mkfs.ext4 timings.
Than, out of curiosity, we increased the G's value to 1048576 and
there was a drastic degradation in the performance of mkfs.ext4.
It took more than 5 minutes to complete the execution.
Is it the expected behavior?
AFAIK flex_bg is on by default with G's vaule as 16. Can we consider
this the optimum value?
Any suggesstions on what we can set the Gs value for a 2TB HDD such
that both the FS and the
mkfs.ext4 gives optimum performance?
It would be really helpful if somebody can shed some light over this feature.
Thanks,
Ashish
On 2012-11-05, at 9:36 PM, Ashish Sangwan wrote:
> We have a 2TB HDD which we formated using default options of mkfs.ext4(v1.42.6).
> I took around ~15 seconds to complete this operation.
>
> Than we formatted the same partition with "-G 1024" and there was
> around 30% performance improvement in
> the mkfs.ext4 timings.
>
> Than, out of curiosity, we increased the G's value to 1048576 and
> there was a drastic degradation in the performance of mkfs.ext4.
> It took more than 5 minutes to complete the execution.
>
> Is it the expected behavior?
The optimum number is very workload specific. We use "-G 256" and
a few other options so that the number of metadata blocks per group
is a multiple of 1MB and aligned on 1MB boundaries. This is for
optimized IO on RAID-6 storage that has good IO performance with 1MB
chunk sizes.
> AFAIK flex_bg is on by default with G's vaule as 16. Can we consider
> this the optimum value?
>
> Any suggesstions on what we can set the Gs value for a 2TB HDD such
> that both the FS and the
> mkfs.ext4 gives optimum performance?
> It would be really helpful if somebody can shed some light over this feature.
>
> Thanks,
> Ashish
Cheers, Andreas