From owner-freebsd-fs@FreeBSD.ORG Sat Feb 18 11:34:00 2012 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 70782106564A for ; Sat, 18 Feb 2012 11:34:00 +0000 (UTC) (envelope-from ronald-freebsd8@klop.yi.org) Received: from smarthost1.greenhost.nl (smarthost1.greenhost.nl [195.190.28.78]) by mx1.freebsd.org (Postfix) with ESMTP id EB0688FC0C for ; Sat, 18 Feb 2012 11:33:59 +0000 (UTC) Received: from [213.108.104.138] (helo=smtp.greenhost.nl) by smarthost1.greenhost.nl with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.69) (envelope-from ) id 1RyiJP-00040i-Nf for freebsd-fs@freebsd.org; Sat, 18 Feb 2012 12:18:44 +0100 Received: from dhcp-077-251-052-224.chello.nl ([77.251.52.224] helo=pinky) by smtp.greenhost.nl with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1RyiJQ-00056R-40 for freebsd-fs@freebsd.org; Sat, 18 Feb 2012 12:18:44 +0100 Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes To: freebsd-fs@freebsd.org References: <20120217141607.GA63659@freebsd.org> <4F3E9A14.3070605@freebsd.org> <20120217190921.GA26568@freebsd.org> Date: Sat, 18 Feb 2012 12:18:45 +0100 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Ronald Klop" Message-ID: In-Reply-To: <20120217190921.GA26568@freebsd.org> User-Agent: Opera Mail/11.61 (Win32) X-Virus-Scanned: by clamav at smarthost1.samage.net X-Spam-Level: / X-Spam-Score: 0.1 X-Spam-Status: No, score=0.1 required=5.0 tests=BAYES_50, RDNS_NONE autolearn=disabled version=3.2.5 X-Scan-Signature: aadb025e1561638fa3cfee7b14734d3b Subject: Re: freebsd-swap on ssd X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Feb 2012 11:34:00 -0000 On Fri, 17 Feb 2012 20:09:21 +0100, Alexander Best wrote: > On Fri Feb 17 12, Julian Elischer wrote: >> On 2/17/12 6:16 AM, Alexander Best wrote: >> >hi there, >> > >> >putting a freebsd-ufs partition on an ssd isn't recommended, since the >> ufs >> >structure (unlike zfs e.g.) requires certain data to be continuously >> >written to >> >a fixed location and thus will cause the ssd to quickly run out of >> >write-cycles >> >and die. >> nonsense. >> the SSD doesn't use the same flash for the same logical locatio each >> time! >> it maps it to different locations each time. > > i simply repeated what kirk mckusick said in the SU+J introduction > video. he > said for exactly this reason ufs should not be used on an ssd, since > stuff like > inode entries live in a fixed location, whereas with zfs the ueberblock > can > live in 128 locations. also in case of SU+J, where the journal only > takes up a > very small part of the disk due to the fact that it's only tracking > metadata > changes and isn't doing logging (like gjournal), there's also the chance > to run > out of write-cycles. A related question. Does journaling make sense on a ssd? I don't think there is a write cache on the ssd. Ronald. > > see: http://youtu.be/_NuhRkiInvA > > cheers. > alex > >> >> >but how about using a small ssd (approx. 10GB) as one entire >> freebsd-swap >> >partition? will this make more sense, or are there certain structures >> >within >> >the freebsd-swap partition type, which also need to be continuously >> >written to >> >a fixed location? >> small SSDs may have less wear resistance than big ones.. the cheap >> ones may not even >> use proper mapping.. >> >another question i'd like to ask: are there also issues with >> read-cycles on >> >ssds? because i was thinking about putting a freebsd-boot partition on >> an >> >ssd >> >drive and only mounting it ro. this should solve the write-cycle issue >> in >> >theory. however i'm not sure, if stuff like the dirty bit or the ufs >> label >> >will >> >also remain untouched. so even though the partition will only be >> mounted >> >ro, >> >freebsd might still frequently write certain data to a fixed location >> on >> >the >> >ssd drive which hosts the freebsd-boot partition. if this is the case, >> is >> >there >> >a way of completely prohibiting any writes to a disk? will revoking any >> >write >> >permissions from the device entry under /dev guarantee this, or is >> using a >> >any >> >device 100% ro under freebsd impossible (unless it has a hardware >> switch to >> >forbid writes)? >> >> yes there are small issues with read cycles but it is all hidden from >> you by the drive. >> >cheers. >> >alex >> >_______________________________________________ >> >freebsd-fs@freebsd.org mailing list >> >http://lists.freebsd.org/mailman/listinfo/freebsd-fs >> >To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >> > > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"