From owner-freebsd-current@FreeBSD.ORG Sun Sep 21 17:39:53 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 68AF6318; Sun, 21 Sep 2014 17:39:53 +0000 (UTC) Received: from smtp2.wemm.org (smtp2.wemm.org [IPv6:2001:470:67:39d::78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "smtp2.wemm.org", Issuer "StartCom Class 1 Primary Intermediate Server CA" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4AA7C21D; Sun, 21 Sep 2014 17:39:53 +0000 (UTC) Received: from overcee.wemm.org (canning.wemm.org [192.203.228.65]) by smtp2.wemm.org (Postfix) with ESMTP id 54D09C16; Sun, 21 Sep 2014 10:39:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wemm.org; s=m20140428; t=1411321192; bh=ylyAJsAj7cNj+mmfQWIEOjuIp/1LRIFUUVtqQ+EmIeg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XRic4ph43LquC8mTpn84wBddun+gcAl4kCyCLXxKEpJYhqNMADy7OCru+K4sbUYAs fCowY8fzqPUzPXqM81EOTno6fNv1kaMOVqk3qZdaclU9xFPD96SQnxj8Md2zfnuimh xTRun+LxTMUyCysev25KebBV/SBepKGh6oyQHR98= From: Peter Wemm To: Steven Hartland Subject: Re: zpool frag Date: Sun, 21 Sep 2014 10:39:43 -0700 Message-ID: <1965644.89SVIqCBMH@overcee.wemm.org> User-Agent: KMail/4.12.5 (FreeBSD/11.0-CURRENT; KDE/4.12.5; amd64; ; ) In-Reply-To: References: <1411289830171-5950788.post@n5.nabble.com> <1691600.4gjp5IhhyR@overcee.wemm.org> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2047581.7hXjsinto4"; micalg="pgp-sha1"; protocol="application/pgp-signature" Cc: freebsd-current@freebsd.org, Allan Jude X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Sep 2014 17:39:53 -0000 --nextPart2047581.7hXjsinto4 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" On Sunday, September 21, 2014 06:12:09 PM Steven Hartland wrote: > ----- Original Message ----- >=20 > > From: "Peter Wemm" > >=20 > > On Sunday, September 21, 2014 11:06:10 AM Allan Jude wrote: > > > On 2014-09-21 04:57, Beeblebrox wrote: > > > > FRAG means fragmentation, right? Zpool fragmentation? That's ne= ws to > > > > me. > > > > If > > > > this is real how do I fix it? > > > >=20 > > > > NAME SIZE ALLOC FREE FRAG EXPANDSZ CAP DEDUP HE= ALTH > > > > ALTROOT pool1 75.5G 53.7G 21.8G 60% - 71% = 1.00x > > > > ONLINE - pool2 48.8G 26.2G 22.6G 68% - 53= %=20 > > > > 1.00x > > > > ONLINE - pool3 204G 177G 27.0G 53% - 86= %=20 > > > > 1.11x > > > > ONLINE - > > >=20 > > > It is not something you 'fix', it is just a metric to help you > > > understand the performance of your pool. The higher the fragmenta= tion, > > > the longer it might take to allocate new space, and obviously you= will > > > have more random seek time while reading from the pool. > > >=20 > > > As Steven mentions, there is no defragmentation tool for ZFS. You= can > > > zfs send/recv or backup/restore the pool if you have a strong eno= ugh > > > reason to want to get the fragmentation number down. > > >=20 > > > It is a fairly natural side effect of a copy-on-write file system= . > > >=20 > > > Note: the % is not the % fragmented, IIRC, it is the percentage o= f the > > > free blocks that are less that a specific size. I forget what tha= t size > > > is. > >=20 > > I fear that the information presented in its current form is going = to > > generate lots of fear and confusion. > >=20 > > The other thing to consider is that this gets much, much worse as t= he pool > > fills up. Even UFS has issues with fragmentation when it fills, bu= t ZFS > > is far more sensative to it. In the freebsd.org cluster we have a = health > > check alert at 80% full, but even that's probably on the high side.= >=20 > This "should" be less of an issue if you have the spacemap_histogram = feature > enabled on the pool, which IIRC if your seeing FRAG details should be= the > case. Hopefully so. The catch though is when its been run without it until r= ecently=20 it can be a bit of a surprise. =2D-=20 Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI= 6FJV UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246 --nextPart2047581.7hXjsinto4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. 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