On 07/04/2013 02:17 PM, Christoph Anton Mitterer wrote: > Hi. > > I'm setting up a 5-bay NAS (based on a QNAP device), with my personal > Debian on it, currently using only 4 devices though > The focus is absolutely on data security/resilience,... and not at all > on performance. This particular statement trumps all other considerations. > Now questions comes, which RAID level to use, and I guess with the main > focus on resilience there's only basically these options: [snip /] You covered all the basics. >From your own analysis, raid6 is the option that maximizes total storage while achieving an "any two failures" resiliency. Triple-copy raid10 across four drives can match that resiliency, with dramatically better performance, but with a substantial cost in capacity. Two-failure resilience is vital to completing recovery after replacing a failed drive, particularly when the read error rates of consumer-grade drives are involved. In your specific case, raid6 has one additional advantage: making future expansion to the fifth bay a reliable, simple, no downtime event. In your situation, I would use raid6. To mitigate the performance hit on occasional random-access work, I would use a small chunk size (I use 16k). That will somewhat hurt peak linear performance, but even bluray-equivalent media streams only amount to 5 MB/s or so. That would be 80 IOPS per device in such a four-drive raid6. Phil -- 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
