On Thu, Dec 10, 2015 at 12:36 AM, Alexander Afonyashin <a.afonyashin@xxxxxxxxxxxxxx> wrote: > Hi, > > Did you set stride/stripe configuration to filesystem that is aligned > with raid configuration? > > Regards, > Alexander > > On Thu, Dec 10, 2015 at 4:34 AM, Dallas Clement > <dallas.a.clement@xxxxxxxxx> wrote: >> Hi all. I'm trying to determine best and worst case expected >> sequential write speeds for Linux software RAID with spinning disks. >> >> I have been assuming on the following: >> >> Best case RAID 6 sequential write speed is (N-2) * X, where is is >> number of drives and X is write speed of a single drive. >> >> Worst case RAID 6 sequential write speed is (N-2) * X / 2. >> >> Best case RAID 5 sequential write speed is (N-1) * X. >> >> Worst case RAID 5 sequential write speed is (N-1) * X / 2. >> >> Could someone please confirm whether these formulas are accurate or not? >> >> >> I am not even getting worst case write performance with an array of 12 >> spinning 7200 RPM SATA disks. Thus I suspect either the formulas I >> am using are wrong or I have alignment issues or something. My chunk >> size is 128 KB at the moment. >> >> Thanks, >> >> Dallas >> -- >> 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 > Did you set stride/stripe configuration to filesystem that is aligned with raid configuration? Hi Alexander. I've just been reading / writing the raw raid device with no filesystem at the moment. Using fio, with direct=1. I seem to get the best results with bs=512k and queue_depth=256. Even with this, I am still short of the worst case write performance. -- 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
