From owner-freebsd-stable@freebsd.org Fri Nov 27 09:42:29 2015 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 503F4A37501 for ; Fri, 27 Nov 2015 09:42:29 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: from mail-wm0-x233.google.com (mail-wm0-x233.google.com [IPv6:2a00:1450:400c:c09::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id D38E91434 for ; Fri, 27 Nov 2015 09:42:28 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: by wmec201 with SMTP id c201so62320100wme.0 for ; Fri, 27 Nov 2015 01:42:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=r/NLQ8e1NyG9o3sW6gl6Ody10SnGlHGBwK9XiAxsiZw=; b=wMeJgTiKqh1boJod05vo8/KHnYBiTrAxpAJR/qGNOb22gfxDE+LIq2/474SScMMxP5 7HejcZ6N0P55sPkG+NLB8o5RtpaRMIXMYfOHmkHhiHEjm/aRNBbSepCWB6FOvn/Cj7tm nD24QJZpDQMqCRFZVvwGRHGRxSLgjiaRLmCITARqhqLILnnlIYerxBLwGDDGC6zKuwDO U8YW0+wCNLoZqWZREb8j0QYOrlr+zCoWQZtb5nDmF02uyCek0rMb1/OdCHNslBykCEK+ Kq1H5WlezoWl98DZJ/wy2yrub0/LgkMhWQY5Ryi1SX5Wwxf1MCkHS0rgpK795sxrs+gq vCCw== MIME-Version: 1.0 X-Received: by 10.28.0.149 with SMTP id 143mr9887227wma.48.1448617346378; Fri, 27 Nov 2015 01:42:26 -0800 (PST) Received: by 10.28.181.213 with HTTP; Fri, 27 Nov 2015 01:42:26 -0800 (PST) In-Reply-To: References: <5654855F.2070502@sentex.net> <20151125081210.6ce3d9404b314fcfb31b061f@aei.mpg.de> <20151125131614.349faf4e6febeb00e401364d@aei.mpg.de> Date: Fri, 27 Nov 2015 09:42:26 +0000 Message-ID: Subject: Re: ZFS - poor performance with "large" directories From: krad To: Freddie Cash Cc: =?UTF-8?B?R2Vycml0IEvDvGhu?= , freebsd-stable Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Nov 2015 09:42:29 -0000 I was referring to the quality of the usb sticks that people have lying around, rather than the port speed. The biggest thing that flash based drives have always don is lower latency, as getting throughput out of magnetic arrays has never been a big issue, random reads/writes a different story though. On 26 November 2015 at 16:32, Freddie Cash wrote: > On Thu, Nov 26, 2015 at 2:19 AM, krad wrote: > >> true, but in my experience usb pen drives are variable in terms of >> performance across different sticks and different areas of the same stic= k. >> This can complicate things a little, and is often not worth the effort. >> You >> obviously run the ssd over usb though, and I still do on one server I ru= n >> 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 e= nough > 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 t= he > 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, lowe= r > latency, smoother system overall). > > =E2=80=8BAs always, YMMV, and test it with your own setup. :)=E2=80=8B > > -- > Freddie Cash > fjwcash@gmail.com >