On May 18, 2015 11:45:32 PM CDT, Adam Goryachev <mailinglists@xxxxxxxxxxxxxxxxxxxxxx> wrote: >On 19/05/15 12:37, Jon Nelson wrote: >> I'm looking for some advise on tuning. >> I have a server with 20 disks behind an LSI 9271-something. >> They are currently exposed as 20 individual raid0 with a "strip" size >> of 1MB, >Ummm, you have 20 disks connected to some raid controller, which >presents them as 20 raid0 arrays? Or are they raid0 arrays consisting >of >only one disk? or JBOD? or something else? > >> and assembled into an mdraid, meta 1.2, layout 10 format f2, >> with a 1MB chunk size and formatted using ext4 -T largefile. >> To date, this has given me the best numbers when reading some 10,000 >> files (total size: about 2.5TB) sequentially or in parallel. > >What other things did you try? >How did you measure this? >What answers did you get? > >> I can't seem to get better than about 1,800 MB/s read speeds though. >I >> *should* be able to get closer to 3,000 based on what the drives are >> capable of. You also need to be aware of controller and bus limits as well as any 10 bit (eg:sas) vs. 8 bit units between the numbers you're seeing, not to mention other overheads in the software end of your storage stack. >> Quite some time ago on this very hardware I saw a >> sustained 2,750 MB/s but I don't remember how I got there. >Are you looking for sequential or random access? You will get very >different numbers for each of these. Also, read vs write, cache hit vs buffered write, etc. >> readahead values have been adjusted, I/O scheduler, etc... all played >> with with some benefit but nothing huge. What should I be looking at >> here if I want the best possible read performance? >> >> I don't want to give up some measure of redundancy. > >The clue here is to test and measure, and keep a record of the results. > >It can be really frustrating when you can't get the same good result >you >had last week. IME, it is a matter of testing something different, and >that is why the result is different. > >Regards, >Adam /me nods Cheers, Brian -- Sent from my mobile device -- 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
