Date: Thu, 26 Nov 2015 08:32:50 -0800 From: Freddie Cash <fjwcash@gmail.com> To: krad <kraduk@gmail.com> Cc: =?UTF-8?B?R2Vycml0IEvDvGhu?= <gerrit.kuehn@aei.mpg.de>, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: ZFS - poor performance with "large" directories Message-ID: <CAOjFWZ7tOjgPMJWrVTz7_sLQq1yj4r6EeGBH4SF4jfcyc3Yy1g@mail.gmail.com> In-Reply-To: <CALfReyczOkhzRaaTD1HCifbddFY3agRP_q7zztNwLLoUKAt_Cw@mail.gmail.com> References: <CAMMK2LCB5ocjyufZCMXQScQDgVxvSHOr0vmef6LKzPO35w3TQg@mail.gmail.com> <CA%2BtpaK3czSuxGH0J%2BVyPRfC8CiGJBk_CPf=bwQzxLjM94RCY9A@mail.gmail.com> <CAMMK2LBCpgb8SPZrC0to9kHHWzFvgvSzaiKjpH-PQm22q%2B=n3g@mail.gmail.com> <5654855F.2070502@sentex.net> <CAMMK2LC2dH2KWgqLS9MfxH7gp1wnqBPrbzEJFWfUDxrtzNG5CQ@mail.gmail.com> <20151125081210.6ce3d9404b314fcfb31b061f@aei.mpg.de> <CALfReycHXjPEzNk1O6kT=TgFb_LQ%2Befd7mzTEZSSF=9gkk%2BGOg@mail.gmail.com> <20151125131614.349faf4e6febeb00e401364d@aei.mpg.de> <CALfReyczOkhzRaaTD1HCifbddFY3agRP_q7zztNwLLoUKAt_Cw@mail.gmail.com>
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On Thu, Nov 26, 2015 at 2:19 AM, krad <kraduk@gmail.com> wrote: > true, but in my experience usb pen drives are variable in terms of > performance across different sticks and different areas of the same stick= . > This can complicate things a little, and is often not worth the effort. Y= ou > obviously run the ssd over usb though, and I still do on one server I run > as I haven't been able to sort the down time yet. > =E2=80=8BNowadays, USB 3.x-based sticks in USB 3.x ports should be fast eno= ugh that they'll be helpful. You won't get the full 5 Gbps from one (unless you spend as much or more than an SSD), but it will be much better than the measly 0.5 Gbps of a USB 2.x stick/port. Don't bother trying with a USB 2.x stick, or with anything plugged into a USB 2.x port. Invariably, it will just slow things down. I used to use 8 GB USB2 sticks in USB2 ports for L2ARC (with a separate one for the root filesystem). When I had 4x IDE disks in a raidz1 vdev=E2=80= =8B, they helped. When I migrated to 4x SATA1 disks in a raidz1 vdev, they helped. When I migrated to 4x SATA3 disks in dual-mirror vdevs (with root-on-ZFS), suddenly the USB stick became the bottleneck. Removing it actually made the whole system faster (better throughput, more IOps, lower latency, smoother system overall). =E2=80=8BAs always, YMMV, and test it with your own setup. :)=E2=80=8B --=20 Freddie Cash fjwcash@gmail.com
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