From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47376) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VoOQZ-0004bP-Nf for qemu-devel@nongnu.org; Wed, 04 Dec 2013 21:12:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VoOQU-0007ol-QZ for qemu-devel@nongnu.org; Wed, 04 Dec 2013 21:12:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37735) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VoOQU-0007o5-Gl for qemu-devel@nongnu.org; Wed, 04 Dec 2013 21:12:26 -0500 Message-ID: <529FE0FF.5040503@redhat.com> Date: Wed, 04 Dec 2013 19:12:15 -0700 From: Eric Blake MIME-Version: 1.0 References: <1385546829-3839-1-git-send-email-pl@kamp.de> <1385546829-3839-9-git-send-email-pl@kamp.de> <20131204164349.GE27759@stefanha-thinkpad.redhat.com> <529F5C56.20906@kamp.de> In-Reply-To: <529F5C56.20906@kamp.de> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="21mjrfCsN1IFAGo7vHGPfbw4LkQgqhJUk" Subject: Re: [Qemu-devel] [PATCHv3 1.8 8/9] qemu-img: increase min_sparse to 128 sectors (64kb) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven , Stefan Hajnoczi Cc: kwolf@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --21mjrfCsN1IFAGo7vHGPfbw4LkQgqhJUk Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 12/04/2013 09:46 AM, Peter Lieven wrote: >> I guess a sane size would be cluster size. For a raw file 4 KB is >> reasonable since that's the file system block size. > in case of iscsi the cluster size could be much too high as for example= > my storage has a cluster_size of 15MB. >> >> Is it necessary to increase to 64 KB here? > No, its indepent of the rest. Paolo suggested to increase it and I can = confirm > that for my usage case its faster than 4K. At least on NTFS file systems, 64k is the minimum size of a hole in a sparse file. While many file systems support smaller holes, there are definitely systems where trying to detect smaller holes only results in wasted efforts. Is it worth making the default dynamic based on stat() information regarding optimum IO size for the given destination file syst= em? --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --21mjrfCsN1IFAGo7vHGPfbw4LkQgqhJUk Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.15 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJSn+EAAAoJEKeha0olJ0NqnVoIAIwJ78f+P4JU//PhblG9cuau R6/GxiYEBhsf6pk4j8iZ5eGcoP1bE2p7QnSlOy8EbPqgfe4Dq34VugZoyj2hfaPs zxRLhilVsiVyHeVTI5O9XpsamtOQn/ZGNTQbi1TgXhVNsXNjDOnb/0iJaXfNkjm8 PSJ4F4uRuPZIQypRWzKTIwGbDDU866GU5DZQ2cGF0BnsGZdVVlyT9RUypOtw8pt8 YvdULkqcZ7TYkmjOYXhfotxGsiGVHny+f0OIAA7YF+/NkVXLKuQHtwDHFko6GuHw G+H59NAgzffpS94V5Klf/8cZVQFtiUdHy3uAlp4zcWrzfMQvwq1HsFTnjCuQChU= =V4Yk -----END PGP SIGNATURE----- --21mjrfCsN1IFAGo7vHGPfbw4LkQgqhJUk--