From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:30957 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbdJFPiG (ORCPT ); Fri, 6 Oct 2017 11:38:06 -0400 Date: Fri, 6 Oct 2017 08:38:03 -0700 From: "Darrick J. Wong" Subject: Re: agcount for 2TB, 4TB and 8TB drives Message-ID: <20171006153803.GI7122@magnolia> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Gandalf Corvotempesta Cc: linux-xfs@vger.kernel.org On Fri, Oct 06, 2017 at 10:46:20AM +0200, Gandalf Corvotempesta wrote: > Hi to all, > i'm new to XFS. > > Which is the proper agcount for 2TB, 4TB and 8TB drives (not part of any RAID) ? > > mkfs.xfs automatically choosen 4 AGs. Isn't this too low ? No. Have a look at calc_default_ag_geometry in libxcmd/topology.c for how we calculate the default AG count / size. 4TB single-disks and smaller get 4 AGs; larger than that get 1AG per TB. RAID arrays are different. Semirelated question: for a solid state disk on a machine with high CPU counts do we prefer agcount == cpucount to take advantage of the high(er) iops and lack of seek time to increase parallelism? (Not that I've studied that in depth.) --D > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html