On Sun, 26 May 2013 19:21:57 -0500, Stan Hoeppner <s...@hardwarefreak.com> wrote:
Hi Stan, hi everybody, > Hopefully I'm teaching not only you, but others, that trying to > optimized performance of a -2 disk- array is a waste of -your- time. I have to say I was a little bit disappointed after this. I took time to read doc' (and there are a lot of). And at the end, even the infos found on the mdadm wiki seems to give a wrong idea of the way to go. > > Docs won't fill in the gaps in your knowledge here. Neither will > running bonnie++, iozone, using 'dd', etc. They simply do not reflect > real world use of a 2 disk RAID1. RAID10,f2 on two disks is simply an > optimization of RAID1 and it's not going to double your throughput. > Whether it is of benefit to your depends entirely on your workload(s). > And with only 2 disks and using the installer, it's pretty clear that > your workload is not 100% single threaded streaming read, which is where > f2 yields the bulk of its benefit. In real world use for a desktop or > most small server workloads, random read/write performance is important, > not sequential read. This is why I said stick with vanilla RAID1. Back to what I read, I have a question: - are RAID0 and RAID10,f2 performances quiet similar in term of random read or not ? - and if there are not, why people are publish these kind of infos on the mdadm wiki ? - moreover, regarding the daily usage of a desktop, does a usefull RAID layout exist to give performances benefit ? > <snip> > > You'll want to go through the installer defaults for all disk counts > before filing such a bug report. There are likely others that many > people would disagree with. If the 3 disk default is RAID5 then ~30 of > users will disagree saying it should be RAID10,f2 for better performance > and redundancy at the cost of space. If it is RAID10,f2 then ~70 > percent will disagree saying the extra space is more important than > redundancy and performance. Advanced users won't care because they'd > -never- use the installer to create their arrays. Advanced users ? I would say experienced users. Because even if you take your time to document yourself, there are few things helping you to take the right decision. But may be I was looking in the wrong direction. > > With only 2 drives, the overall performance difference between RAID1 and > RAID10,f2 is nearly statistically even, with real world workloads. So > to reiterate my previous point, it is a waste of -your- time attempting > to figure out which one is slightly faster. It is your time to waste, > so go ahead if you like. I'm simply trying to save you some that can be > put to better use elsewhere. > Anyway, I am busy setting up some small VMs to test some services within isolated environments. I was thinking running them on my small partition using different RAID layouts to see how it behaves in real world. It will cost nothing extra and will help me to get ... more experienced. :-) Anyway, thank you for all the infos you gave through this exchange. > -- > Stan Jean-Marc <jean-m...@6jf.be> -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1294ce3971c386f0a81d8ab2ec9c9798@localhost
