On Wed, Nov 13, 2013 at 6:13 AM, Matthew Patton <pattonme@xxxxxxxxx> wrote: > On Wed, 13 Nov 2013 03:42:54 -0500, Francis Moreau <francis.moro@xxxxxxxxx> > wrote: > >> First I'd like to know if over-provisioning is still needed when >> bcache is used ? > > > it's needed for any decent, sustained write load if you don't want > performance to crash thru the floor. But it doesn't sound like this is your > use case. Are you sustaining 5000+ write IOPs? > > >> - Should I create 2 partitions with one left emtpy and whose size is >> roughly 7% of the device size ? > bcache has a pretty flash friendly write pattern, so you probably don't need a huge lot of empty space. The 7% might in fact be enough, but bumping it up to 10%-12% wouldn't hurt. I think the >25% numbers are more relevant for non-flash friendly writes (like random writes). In that case you definitely want lots of free space. > > Your SSD already has 7% overprovisioning. For best sustained and consistent > write performance you'll want to bump it to 25-30%. Yes you just need to > partition/LVM down to the desired size. > > >> - Should I create a "Host Protected Area" by using hdparm ? > > > http://www.thomas-krenn.com/en/wiki/SSD_Over-provisioning_using_hdparm > > Either take the precautions outlined in the WIKI given the penchant of the > kernel to ignore such settings, or just remove the chance for error and > partition the device instead. > > >> And finally, can I create the over-provisioning without lost the >> content of my backing device ? > > > hell no. > > -- > NSA - subscribe to our Timeline and you'll know even before they've hit > 'ENTER' > > "The budget should be balanced, the Treasury refilled, public debt reduced, > the arrogance of officialdom tempered and controlled, and the assistance to > foreign lands should be curtailed lest Rome become bankrupt. People must > again learn to work, instead of living on public assistance." > - Cicero (55 BC) > > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
