From owner-freebsd-fs@freebsd.org Thu May 6 13:52:02 2021 Return-Path: Delivered-To: freebsd-fs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id A35EC6224E5 for ; Thu, 6 May 2021 13:52:02 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mailman.nyi.freebsd.org (unknown [127.0.1.3]) by mx1.freebsd.org (Postfix) with ESMTP id 4FbZkp28gFz4htF for ; Thu, 6 May 2021 13:52:02 +0000 (UTC) (envelope-from asomers@gmail.com) Received: by mailman.nyi.freebsd.org (Postfix) id 49F0A622671; Thu, 6 May 2021 13:52:02 +0000 (UTC) Delivered-To: fs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 49B2B622670 for ; Thu, 6 May 2021 13:52:02 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mail-ot1-f53.google.com (mail-ot1-f53.google.com [209.85.210.53]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4FbZkp1bKSz4j58 for ; Thu, 6 May 2021 13:52:01 +0000 (UTC) (envelope-from asomers@gmail.com) Received: by mail-ot1-f53.google.com with SMTP id i23-20020a9d68d70000b02902dc19ed4c15so913951oto.0 for ; Thu, 06 May 2021 06:52:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5bDjjaLejB/FFxFO86S0e21vO14fqvuR//weUKIG7Ro=; b=oAB5mwFr8KSnsNTZiejbdncXCFqrOvuXndP72qyfsKZPw7sWTDM/RIciNhXdF3uZB7 qa0ONdsemHS+tygiwIX40LzJFH1gHUo3BDM3DRoIfO2NlzhuNnXurDvxml3d/c+sdOgR bpyzEks8kmkJDg72dXWSLjL1lihhIqqpi6kYINkty6W9ipAuFv94srLtX2sL4dWjhWy4 YaUpwxH1XQP2TDPzbH7zvFDgaIRT7rbIP/8r3FfXeUK7cIoA4jAwplDj8LvFMOl+Cy87 sbMbobIIrKHrnNmI9dH9Gk4fX4z6ZS11ROGNVhdUoV01EbAivyYO/z0C9/SvQQFD1tFS 0Lhw== X-Gm-Message-State: AOAM5317BXJZ9cye7STDHuOlm6ihcrpyJGyxT5z+z6s2f+CEiHl56nM0 6J/1sTDWG1HYw8ui+CKmdocS3G7bzlX2PslkrGE= X-Google-Smtp-Source: ABdhPJxSn3aQ4j7MXJ21Mq379zT4bOdvPDwbZFUbpEAkMFlqJs47tDNVlIUewJA8X7tTJ+L5EJNNFbEr1BI44esl7TU= X-Received: by 2002:a9d:7d90:: with SMTP id j16mr3751641otn.18.1620309120905; Thu, 06 May 2021 06:52:00 -0700 (PDT) MIME-Version: 1.0 References: <578487FF-1D89-4A9E-AD97-6B5DCD9F785A@gmx.com> <62B46E11-A40C-4119-8525-20E3F3539D61@gmx.com> In-Reply-To: <62B46E11-A40C-4119-8525-20E3F3539D61@gmx.com> From: Alan Somers Date: Thu, 6 May 2021 07:51:49 -0600 Message-ID: Subject: Re: Dual-port SAS HDD ? To: Ben RUBSON Cc: "fs@freebsd.org" X-Rspamd-Queue-Id: 4FbZkp1bKSz4j58 X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.34 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 06 May 2021 13:52:02 -0000 On Thu, May 6, 2021 at 7:37 AM Ben RUBSON wrote: > > On 6 May 2021, at 15:24, Alan Somers wrote: > > > > On Thu, May 6, 2021 at 4:52 AM Ben RUBSON ben.rubson@gmx.com>> wrote: > > Hi, > > > > I'm building a new ZFS pool from scratch, choosing my own hardware etc... > > For sure I'll go for the standard SAS2008 / SAS3008 controller. > > > > However, I'm wondering whether or not I should absolutely go for > dual-port SAS HDD (with dual backplane, controller...). > > I have some difficulties to find enterprise grade dual port SAS HDD. > > HGST used to provide Ultrastar SAS HDD which were dual-port. > > However, strangely, Western Digital does not advertise their Ultrastar > DC SAS HDD as bringing dual-port, so I guess they're not. > > > > Any thoughts / advices regarding this topic ? > > > > Many thanks for your help, > > > > Kind regards, > > > > Ben > > > > It's just a matter of high availability. Can you tolerate an outage if > a JBOD I/O controller fails? If so, then you don't need dual-port. But > server crashes are more common than JBOD I/O controller failures. So you > should worry more about that. > > Thank you Alan. > Of course you're right, JBOD IO controller is not the first outage cause, > and disks themselves are more prone to fail... > > I even wonder whether or not dual path is actively used for HDDs, as > dual-port ones are rather hard to find... > Not sure then it's really worth it... > > Of course feel free if I'm wrong / I missed something / one actively uses > it and has some experience / references to share ! > > Thank you again, > > Ben > Sure, dual paths are actively used. They work well with gmultipath, which is how I use them. And AFAIK all SAS drives are dual-ported. Western Digital describes their drives as "dual port" on this site: https://www.westerndigital.com/products/data-center-platforms/ultrastar-sas-series-ssd