> On Sep 15, 2017, at 6:59 AM, lejeczek <[email protected]> wrote: > > > On 15/09/17 03:20, Brassow Jonathan wrote: >> There is definitely a difference here. You have 2 stripes with 5 devices in >> each stripe. If you were writing sequentially, you’d be bouncing between >> the first 2 devices until they are full, then the next 2, and so on. >> >> When using the -i argument, you are creating 10 stripes. Writing >> sequentially causes the writes to go from one device to the next until all >> are written and then starts back at the first. This is a very different >> pattern. >> >> I think the result of any benchmark on these two very different layouts >> would be significantly different. >> >> brassow >> >> BTW, I swear at one point that if you did not provide the ‘-i’ it would use >> all of the devices as a stripe, such that your two examples would result in >> the same thing. I could be wrong though. >> > that's what I thought I remembered too. > I guess a big question, from user/admin perspective is: are those two stripes > LVM decides on(when no -i) is the best possible choice LVM makes after some > elaborative determination so the number of stripes(no -i) would, might vary > depending on raid type, phy devices number and maybe some other factors or, 2 > stripes are simply hard-coded defaults?
If it is a change in behavior, I’m sure it came as the result of some changes in the RAID handling code from recent updates and is not due to some uber-intellegent agent that is trying to figure out the best fit. brassow _______________________________________________ linux-lvm mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
