On 10/01/17 08:48, Benjammin2068 wrote: > Most of the major CCTV systems suffer in the same way, and they generally get around it by using "hardware" RAID cards with large RAM buffers (until the BBU wears out and you start getting massive footage loss because they can't get the streams to disk fast enough). >> >> If performance is not an issue then a RAID6 being written from a Windows VM on a Linux host works just fine. Pass the md straight through to the Windows VM and let it manage the raw block device. This made me think. Bear in mind ext tends to over-allocate space to try and avoid fragmentation. I don't know to what extent it happens automatically, but this sounds similar to what Brad is recommending. If you can match your file system to your raid array, such that the file-system's default allocation unit is one stride of the raid, this will help avoid RMW thrashing. Pretty obvious, in hindsight, this will mean strides (mostly) never get split across files so are only ever allocated and freed as whole units. Cheers, Wol -- 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
