On 12/17/2013 4:40 AM, Nikolaus Jeremic wrote: > Hi, > > I've did some Linux MD RAID 5 and 6 random write performance tests with > fio 2.1.2 (Flexible I/O tester) under Linux 3.12.4. However, the results > for RAID 6 show that writes to a single chunk in a stripe (chunk size is > 64 KB) result in more than 3 reads in case of more than 6 drives (tested > with 7, 8, and 9 drives) in the array (see fio statistics below). It > seems like that in the event of updating one data chunk in a stripe, all > of the remaining data chunks are read. > > By the way, in case of RAID 5 and 5 or more drives, the remaining chunks > seem not to be read when updating a single chunk in a stripe. > > Here is the fio job description: <snip> It would be easier and more deterministic if you'd simply use dd to write one full stripe, then seek to one chunk within that stripe and write one page. -- Stan -- 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
