From owner-freebsd-questions@freebsd.org Mon Dec 18 16:26:31 2017 Return-Path: Delivered-To: freebsd-questions@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 5CCF3E98164 for ; Mon, 18 Dec 2017 16:26:31 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-wr0-x241.google.com (mail-wr0-x241.google.com [IPv6:2a00:1450:400c:c0c::241]) (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 E13D625EB for ; Mon, 18 Dec 2017 16:26:30 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: by mail-wr0-x241.google.com with SMTP id h1so14674987wre.12 for ; Mon, 18 Dec 2017 08:26:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=jxfKHn8ffXqF7r98AqdzRz42FanoSq2saoH5A8tskd0=; b=pFZn5g3uMNLqVshlytjZNmhoOzzt7jjGmxkWQBcQj9YlTQ16/bj8T/q0Xi+xWqyt0B eECnl7hyecxubNdTEMDbLx4P/jgJLT2sEhR8bjQUtC+w+5HRJjD9Bf+stGuIAg9W2/2v KF47DvQAP1HVLQAeZFslETQO4CYex/Z6bR8eD3K2cCLeENODGOi0k3XUM8U8qQpC86Yl xPO3Fleo2oG6CvWUL8QGr1Wz2LpdDbeJETOu1M96YEb+nF35hRJJ5MGW19Cz6c3jl7zE 813dN2vhinY0yNLWBvO+FdLnhOor4eEUDeGTRLgrt/lhJhCAvGvN1tnAKkZT1g9kRsfM IIBQ== X-Gm-Message-State: AKGB3mLZavghSJlM4y1/QdPcB4Kl2HrraevvIHWveATozfvFM86DNC1T Fq48Ci/gI0qJnCOqVqSHwIXJwA== X-Google-Smtp-Source: ACJfBosDTucKGz++4aOgbdLzkKU3PNtau5w+wZOKmlVJIcb3g3v010EBmwANekVARhD8GgmOSi2TrQ== X-Received: by 10.223.168.48 with SMTP id l45mr361565wrc.261.1513614389067; Mon, 18 Dec 2017 08:26:29 -0800 (PST) Received: from gumby.homeunix.com ([81.17.24.158]) by smtp.gmail.com with ESMTPSA id w51sm11235512edd.84.2017.12.18.08.26.27 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Dec 2017 08:26:28 -0800 (PST) Date: Mon, 18 Dec 2017 16:26:25 +0000 From: RW To: freebsd-questions@freebsd.org Subject: Re: hd firecuda Message-ID: <20171218162625.5bcc543e@gumby.homeunix.com> In-Reply-To: <20171218085219.2fec7c3b.freebsd.ed.lists@sumeritec.com> References: <1513447749.62024.1.camel@yandex.com> <20171217112428.150d8041.freebsd.ed.lists@sumeritec.com> <20171217111319.6a1af590@gumby.homeunix.com> <20171217194753.3ab59e6d.freebsd.ed.lists@sumeritec.com> <20171217150007.642efc20@gumby.homeunix.com> <20171218085219.2fec7c3b.freebsd.ed.lists@sumeritec.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; amd64-portbld-freebsd11.1) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Dec 2017 16:26:31 -0000 On Mon, 18 Dec 2017 08:52:19 +0800 Erich Dollansky wrote: > Hi, > > On Sun, 17 Dec 2017 15:00:07 +0000 > RW via freebsd-questions wrote: > > > On Sun, 17 Dec 2017 19:47:53 +0800 > > Erich Dollansky wrote: > > > > > > > > My understanding is they weren't intended to work like that. The > > > > last I heard was that the SSD was divided into two, one part > > > > specifically speeds up booting, and the other part caches > > > > sectors where the head had to seek to access a small amount of > > > > data. > > > > > > how should a hard disk work? Data is written, data is read. > > > > > > How should this SSHD know where by boot-related data is > > > stored? > > > > It knows when you boot, it knows the sequence of sectors that were > > accessed after boot and it can keep statistics about which are > > accessed on multiple boots. > > how often do you boot your FreeBSD machine before installing a new > kernel? If I boot a machine five times before installing a new kernel, > the number is high. The details of precisely which sectors are cached is not important (although it is important to recognise that Seagate doesn't care about how these devices perform under FreeBSD). What I'm getting at is that previous version of these devices did selective read caching - not write caching. I don't see any reason to think that this has changed - especially when their marketing isn't mentioning it. Even if they are now doing write caching, it's very unlikely that anything like the full 8GB of flash would available for it because you wouldn't want saving a 10GB video file to blow-away the cache.