From owner-freebsd-fs@freebsd.org Wed Aug 19 16:03:09 2015 Return-Path: Delivered-To: freebsd-fs@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 C0FA09BE84D for ; Wed, 19 Aug 2015 16:03:09 +0000 (UTC) (envelope-from chip@innovates.com) Received: from mail-pd0-f175.google.com (mail-pd0-f175.google.com [209.85.192.175]) (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 9BD897B3 for ; Wed, 19 Aug 2015 16:03:09 +0000 (UTC) (envelope-from chip@innovates.com) Received: by pdbfa8 with SMTP id fa8so3075696pdb.1 for ; Wed, 19 Aug 2015 09:03:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-type; bh=F8M8yu6EO+ymv8Z1h0z19+RyPV+Ybl+ixrJWKts5/6k=; b=Jhnm1oHjESRkwz2ld131ckL7YAgN0s5PA+gQQDfpuUlbscfZrikoWJXaYxpA/CGsc2 pRLRJ398IjVQ1HBAqRplHqMaDN8+CUKGwl0eNX5ciI0mIoaX5jr95lx+V9GUOEWe9GC4 Ti1hAyMZY5Fa9gtV+v0whOGL0LwdpHsF/RKu0YU1ITn0/FnJiMHbkGC9wznsF7Nvdq2H 3B3REp3VmaxyqmYT+IlRiy3QtOG9qAcSM+XPjz+wNmRMT3t4aTRg0mbcyYDVBsNANbOB ofweAK+56pBHtyYsafZvx3WqAw7MRBoaFrptL3bUXCk9mbj2Ybgeb9bqy6BGTgeH3gDV 8Nsg== X-Gm-Message-State: ALoCoQmfA6sdTYvLd7tWsMQfJDTXd/1ZgL9X7pmlOAgAO3W2VY8E3BYmESiMPlSN357FzerzlpEF X-Received: by 10.70.137.37 with SMTP id qf5mr10797912pdb.12.1440000183679; Wed, 19 Aug 2015 09:03:03 -0700 (PDT) MIME-Version: 1.0 Received: by 10.66.162.196 with HTTP; Wed, 19 Aug 2015 09:02:44 -0700 (PDT) X-Originating-IP: [128.252.11.235] In-Reply-To: <023F881D-CCC5-4FCA-B09D-EB92C3BFBC03@pk1048.com> References: <023F881D-CCC5-4FCA-B09D-EB92C3BFBC03@pk1048.com> From: "Schweiss, Chip" Date: Wed, 19 Aug 2015 11:02:44 -0500 Message-ID: Subject: Re: Optimizing performance with SLOG/L2ARC To: PK1048 Cc: javocado , FreeBSD Filesystems Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Aug 2015 16:03:09 -0000 On Wed, Aug 19, 2015 at 10:29 AM, PK1048 wrote: > > Please note that, depending on your workload, an SSD may _not_ be any > faster than a HDD. I am in the process of rebuilding a file server that > exhibited poor NFS SYNC write performance. Yet it had a mirrored pair of > SSDs. Unfortunately, those SSDs had _worse_ write performance than an HDD > for small (4 KB) writes. Based on recommendations from the OpenZFS list I > have a pair of Intel 3710 SSDs coming in to try, they are supposed to hav= e > much better write performance (at all block sizes) and much better > reliability long term (10x full disk writes per day for 5 years). I=E2=80= =99ll know > more once they arrive and I can test with them. > Pure SSD pools still need a log device. ZFS doesn't play well with the ZIL on the pool with SSDs. Even an SSD of the same type as the pool devices as the log device will fix the latency problem and throughput problems. It seems counter-intuitive but a very real problem, there is a long thread about this on the Illumos ZFS list. If you don't believe it, turn off sync on your SSD pool and performance will skyrocket. -Chip