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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
