From owner-freebsd-fs@freebsd.org Mon Nov 30 09:17:36 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 E27CEA3C686 for ; Mon, 30 Nov 2015 09:17:36 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: from mail-wm0-x236.google.com (mail-wm0-x236.google.com [IPv6:2a00:1450:400c:c09::236]) (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 829DD151B for ; Mon, 30 Nov 2015 09:17:36 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: by wmvv187 with SMTP id v187so146169741wmv.1 for ; Mon, 30 Nov 2015 01:17:34 -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=+0Ka9EXzJkn6Axjlnp6TLG61ZvXGmietG5TCK0vgiCI=; b=b8oT1Q+YlNtfomyxt8VlMnhW9skCe2/J4qO+9basMNtPfxtmGJsNUAiB44vcb50hjt QA4KVbOUVnQXivifDegMosCuaJNQSF/38z0J4sXgkkAJ8ehi5W6y1Y9SEb/dmhVyPQCH vyuJYGb1gVl7gWKjMo+biJ4tkIGuAcXDv0I+vSZbrSaB4+v2lWkY+y4daF9ChNpCZ6z2 I+hdrmk5k3BAKCVYMBXjRx0KxmCRjBla1a9eMvlCmJqylc0/9sTmvRMLVu9ZNH2GeFVf sD6hr2NBBxKy/6cxAtckIdKEK15Xwzq+fIXXjMKGZ5cT9bijGTadytNvUO7R8E2JeEkK OK+Q== MIME-Version: 1.0 X-Received: by 10.194.236.228 with SMTP id ux4mr10632467wjc.56.1448875054050; Mon, 30 Nov 2015 01:17:34 -0800 (PST) Received: by 10.28.181.213 with HTTP; Mon, 30 Nov 2015 01:17:33 -0800 (PST) In-Reply-To: <565875A7.6060004@free.de> References: <565875A7.6060004@free.de> Date: Mon, 30 Nov 2015 09:17:33 +0000 Message-ID: Subject: Re: High fragmentation on zpool log From: krad To: Kai Gallasch Cc: FreeBSD FS Content-Type: text/plain; charset=UTF-8 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: Mon, 30 Nov 2015 09:17:37 -0000 Fragmentation isn't really a big issue on SSD's as there are no heads to move around like on magnetic drives. Also due to wear levelling, you actually have no idea where a block actually is on a memory cell, as the drive only gives a logical representation of the layout of blocks, not an actual true mapping. On 27 November 2015 at 15:24, Kai Gallasch wrote: > > Hi. > > Today I had a look at the zpool of a server (FreeBSD 10.2, GENERIC > kernel, 100d uptime, 96GB RAM) I recently installed. > > The pool has eight SAS drives in a raid 10 setup (concatenated mirror > pairs) and uses a cache and a mirrored log. > > The log and cache both are on a pair of Intel SSDs. > > # gpart show -l da9 > => 34 195371501 da9 GPT (93G) > 34 6 - free - (3.0K) > 40 16777216 1 log-BTTV5234003K100FGN (8.0G) > 16777256 178594272 2 cache-BTTV5234003K100FGN (85G) > 195371528 7 - free - (3.5K) > > > Is 85% fragmentation of the log device something to worry about? > > Why does zpool list show so unrealistic values for FREE and CAP? > Is this normal? > > Atached: Some output of zpool list. > > Regards, > Kai. > > > (zpool list -v output, ommited columns: EXPANDSZ.,DEDUP, > HEALTH, ALTROOT) > > NAME SIZE ALLOC FREE FRAG CAP > rpool 7.25T 440G 6.82T 4% 5% > mirror 1.81T 110G 1.71T 4% 5% > gpt/rpool-WMC160D0SVZE - - - - - > gpt/rpool-WMC160D8MJPD - - - - - > mirror 1.81T 110G 1.70T 4% 5% > gpt/rpool-WMC160D9DLL2 - - - - - > gpt/rpool-WMC160D23CWA - - - - - > mirror 1.81T 110G 1.71T 4% 5% > gpt/rpool-WMC160D94930 - - - - - > gpt/rpool-WMC160D9V5LW - - - - - > mirror 1.81T 110G 1.71T 4% 5% > gpt/rpool-WMC160D9ZV0S - - - - - > gpt/rpool-WMC160D5HFT6 - - - - - > mirror 7.94G 43.2M 7.90G 85% 0% > gpt/log-BTTV523401U4100FGN - - - - - > gpt/log-BTTV5234003K100FGN - - - - - > cache - - - - - > gpt/cache-BTTV5234003K100FGN 85.2G 142G 16.0E 0% 166% > gpt/cache-BTTV523401U4100FGN 85.2G 172G 16.0E 0% 202% > > > > -- > PGP-KeyID = 0x70654D7C4FB1F588 > > > >