L2ARC uses the ZIO pipeline, just like everything else. Very parallel. But if your workload isn’t parallel, then...
-- richard > On Aug 23, 2018, at 7:03 PM, Jason Matthews <ja...@broken.net> wrote: > > > In 1989 a 4mb stick of ram was like $800. RAM is cheap despite price fixing. > > Having recently maxed out the 64mb of RAM on my personal IPX in like 1994, I > remember telling Len Rose I can’t imagine having a gigabyte of RAM. He > laughed at me. > > Now I sit on racks of systems with 768gb of RAM. RAM is cheap. > > J. > > Sent from my iPhone > >> On Aug 23, 2018, at 6:08 PM, Rich via openzfs-developer >> <developer@lists.open-zfs.org> wrote: >> >> Not every board can take ass-tons of RAM, and DDR4 RAM prices have >> gone markedly up in the last 2 years, not down. (There's even a fun >> price-fixing lawsuit or two in the works.) >> >> You'd also need to buy a decently high-end chip to exceed 128 GB of >> RAM on your server. >> >> So while I agree the need for L2ARC in a number of situations has gone >> down, it's hardly limited to the "highly budget oriented plays." >> >> - Rich >> >>> On Thu, Aug 23, 2018 at 8:42 PM, Jason Matthews <ja...@broken.net> wrote: >>> >>> Maybe I am doing it wrong but I am using NVMe for primary storage and ass >>> tons of ram for arc. >>> >>> I think L2ARC is relegated to the highly budget oriented plays these days as >>> RAM is soooo cheap. Buy some more ram and fooor-get-about it. >>> >>> J. >>> >>> Sent from my iPhone >>> >>> On Aug 23, 2018, at 1:07 PM, Sanjay Nadkarni <sanjay.nadka...@nexenta.com> >>> wrote: >>> >>> Found this link for FreeBSD too >>> http://www.brendangregg.com/blog/2015-03-10/freebsd-flame-graphs.html >>> >>> -Sanjay >>> >>> >>> >>> On 8/23/18 1:02 PM, Sanjay Nadkarni wrote: >>> >>> Would be useful if you could get flamegraphs when you run into this. See >>> https://github.com/brendangregg/FlameGraph >>> >>> Once we have that, the we can have a better understanding of what's going on >>> and we can dtrace it further to figure it out. >>> >>> -Sanjay >>> >>> >>> >>> On 8/23/18 5:47 AM, w.kruzel via openzfs-developer wrote: >>> >>> It's interesting what you said, as I have two examples (both with different >>> Intel nvme disks) that show otherwise. >>> >>> Being nvme, I was expecting read performance from L2ARC at 2GB/s+ levels, >>> yet I only get ~200MB/s read speeds when I certainly know it is being read >>> from L2ARC. >>> >>> When tested (details in my earlier post), I can get the same speed with >>> nvmecontrol perftest that is single threaded. >>> Multi threaded perftest gives 2GB/s + output. >>> >>> I also have this raised with FreeNAS where one of their devs tested it on >>> other make L2ARC he had installed and confirmed that it looks like single >>> threaded process. >>> >>> Can someone look into this please? >>> It is a major performance hit for L2ARC, making it not really fit for >>> purpose :( >>> >>> Kind regards, >>> Wojciech Kruzel >>> >>> >>> >>> openzfs / openzfs-developer / see discussions + participants + delivery >>> options Permalink ------------------------------------------ openzfs: openzfs-developer Permalink: https://openzfs.topicbox.com/groups/developer/Tf62628db027682f7-M658226abcd72e10176704f0d Delivery options: https://openzfs.topicbox.com/groups/developer/subscription
