On 23.07.2010 08:10, Stan Hoeppner wrote: > Michael Monnerie put forth on 7/23/2010 5:59 AM: > > On Freitag, 23. Juli 2010 Christoph Hellwig wrote: > >> -b size=4096 is the default anyway, for 4k sector drivers you also > >> want -s size=4096, which you do not want for 512 byte sector disks. > > > > Thanks for clarification. Should I use "-s size=4096" despite the drive > > saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring > > it extra for XFS helps performance? Or does it not matter at all? > > > >> What values do the files > >> > >> /sys/block/<device>/queue/logical_block_size > >> /sys/block/<device>/queue/physical_block_size > >> /sys/block/<device>/alignment_offset > >> > >> say about your disk? > > > > 512, 512, 0 for a Western Digital D20EARS-00MVWB0 (2TB) which has 4K > > sectors but obviously hides it. > > The WD20EARS-00MVWB0 is definitely a 4k sector drive: > http://products.wdc.com/Library/Flyer/ENG/2178-771123.pdf > > If you're currently seeing somewhere between 60-120MB/s per drive with hdparm > or dd then you don't need to further tweak anything. If alignment is off, > from all I've read, performance will be abysmal, down in the sub 30MB/s range. Only for writes, reads are for practically unaffected. The problem for write is the "Read Modify Write" Cycle that is needed when you don't change all 8 512byte "sub-"sectors contained in a 4096 byte sector. Bis denn -- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
