Am 20.06.2013 21:10, schrieb Mark Knecht: > Hi, > Does anyone know of info on how the starting sector number might > impact RAID performance under Gentoo? The drives are WD-500G RE3 > drives shown here: > > http://www.amazon.com/Western-Digital-WD5002ABYS-3-5-inch-Enterprise/dp/B001EMZPD0/ref=cm_cr_pr_product_top > > These are NOT 4k sector sized drives. > > Specifically I'm a 5-drive RAID6 for about 1.45TB of storage. My > benchmarking seems abysmal at around 40MB/S using dd copying large > files. It's higher, around 80MB/S if the file being transferred is > coming from an SSD, but even 80MB/S seems slow to me. I see a LOT of > wait time in top. And my 'large file' copies might not be large enough > as the machine has 24GB of DRAM and I've only been copying 21GB so > it's possible some of that is cached. > > Then I looked again at how I partitioned the drives originally and > see the starting sector of sector 3 as 8594775. I started wondering if > something like 4K block sizes at the file system level might be > getting munged across 16k chunk sizes in the RAID. Maybe the blocks > are being torn apart in bad ways for performance? That led me down a > bunch of rabbit holes and I haven't found any light yet. > > Looking for some thoughtful ideas from those more experienced in this area. > > Cheers, > Mark > >
man mkfs.xfs man mkfs.ext4 look for stripe size etc. Have fun.
