On Thu, 24 Mar 2011 00:52:00 -0500 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote: > If you write a file much smaller than the stripe size, say a 1MB file, > to the filesystem atop this wide RAID10, the file will only be striped > across 16 of the 192 spindles, with 64KB going to each stripe member, 16 > filesystem blocks, 128 sectors. I don't know about mdraid, but with > many hardware RAID striping implementations the remaining 176 disks in > the stripe will have zeros or nulls written for their portion of the > stripe for this file that is a tiny fraction of the stripe size. This doesn't make any sense at all. No RAID - hardware or otherwise - is going to write zeros to most of the stripe like this. The RAID doesn't even know about the concept of a file, so it couldn't. The filesystem places files in the virtual device that is the array, and the RAID just spreads those blocks out across the various devices. There will be no space wastage. If you have a 1MB file, then there is no way you can ever get useful 192-way parallelism across that file. Bit if you have 192 1MB files, then they will be spread even across your spindles some how (depending on FS and RAID level) and if you have multiple concurrent accessors, they could well get close to 192-way parallelism. NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
