From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 8846 invoked from network); 6 Mar 2021 01:17:20 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 6 Mar 2021 01:17:20 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 7547B9CA91; Sat, 6 Mar 2021 11:17:19 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id B92CF9CA6D; Sat, 6 Mar 2021 11:16:55 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 7838B9CA6D; Sat, 6 Mar 2021 11:16:52 +1000 (AEST) Received: from lax.lemis.com (www.lemis.com [45.32.70.18]) by minnie.tuhs.org (Postfix) with ESMTP id 41DCB9CA6B for ; Sat, 6 Mar 2021 11:16:51 +1000 (AEST) Received: from eureka.lemis.com (unknown [121.200.11.253]) by lax.lemis.com (Postfix) with ESMTP id 9D0C9280AF; Sat, 6 Mar 2021 01:16:50 +0000 (UTC) Received: by eureka.lemis.com (Postfix, from userid 1004) id 553892635BE; Sat, 6 Mar 2021 12:16:49 +1100 (AEDT) Date: Sat, 6 Mar 2021 12:16:48 +1100 From: Greg 'groggy' Lehey To: John Gilmore Message-ID: <20210306011648.GA80491@eureka.lemis.com> References: <20210304212459.GA6303@eureka.lemis.com> <20210304212917.GB6303@eureka.lemis.com> <25189.1614937832@hop.toad.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="IS0zKkzwUGydFO0o" Content-Disposition: inline In-Reply-To: <25189.1614937832@hop.toad.com> Organization: LEMIS, 29 Stones Road, Dereel, VIC, Australia Phone: +61-3-5309-0418 Mobile: +61-490-494-038. Use only as instructed. WWW-Home-Page: http://www.lemis.com/grog X-PGP-Fingerprint: 9A1B 8202 BCCE B846 F92F 09AC 22E6 F290 507A 4223 User-Agent: Mutt/1.6.1 (2016-04-27) Subject: Re: [TUHS] tunefs -m 5% X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: TUHS main list Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" --IS0zKkzwUGydFO0o Content-Type: text/plain; charset=us-ascii Content-Disposition: inline I haven't redirected this reply to COFF, though I was considering doing so: it On Friday, 5 March 2021 at 1:50:32 -0800, John Gilmore wrote: > John P. Linderman wrote: >> I have several 12 TB disks scattered about my house. 5% of 12TB is 600GB. > > At one point in hystery, ext2 performance was reported to suffer badly > if there was less than 5% of disk space available in an active > filesystem. My naive belief, probably informed by older and wiser heads > around Sun, was that when the file system was >95% full, ext2 spent a > lot of time seeking around in free lists finding single allocatable > blocks. And there were no built-in "defragmentation" programs that > could easily fix that. This appears to have been inherited from UFS. My recollection is pretty much the same for UFS, and even the man page entry for EXT4 is closely related to UFS newfs(8): Linux: -m reserved-blocks-percentage Specify the percentage of the filesystem blocks reserved for the super-user. This avoids fragmentation, and allows root-owned daemons, such as syslogd(8), to continue to function correctly after non-privileged processes are prevented from writing to the filesystem. The default percentage is 5%. FreBSD: -m free-space The percentage of space reserved from normal users; the minimum free space threshold. The default value used is defined by MINFREE from , currently 8%. See tunefs(8) for more details on how to set this option. And I can confirm that file systems slow down significantly after the last 1% of free space has been used. > Is that still a performance constraint in ext4, which has had a few > decades to work out those edge performance issues? Hopefully Ted will comment. But UFS has had even more decades. And arguably 600 GB on a modern disk is less of a concern than 15 MB on a 300 MB disk 40 years ago. Greg -- Sent from my desktop computer. Finger grog@lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA --IS0zKkzwUGydFO0o Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAmBC2AAACgkQIubykFB6QiOPbgCfZPJ8f0V+zhUddTxoNZlo5++A 8MwAn1FFGMAmwqhTHW3/lQHjWpE3Hrdq =v4hF -----END PGP SIGNATURE----- --IS0zKkzwUGydFO0o--