From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q75KQ7iv002896 for ; Sun, 5 Aug 2012 15:26:08 -0500 Received: from greer.hardwarefreak.com (mo-65-41-216-221.sta.embarqhsd.net [65.41.216.221]) by cuda.sgi.com with ESMTP id LyTwVzvfE1Un1xpw for ; Sun, 05 Aug 2012 13:26:06 -0700 (PDT) Message-ID: <501ED6E0.802@hardwarefreak.com> Date: Sun, 05 Aug 2012 15:26:08 -0500 From: Stan Hoeppner MIME-Version: 1.0 Subject: Re: xfs_growfs / planned resize / performance impact References: <5017E426.2040709@profihost.ag> <201208051303.09337.Martin@lichtvoll.de> <501E6872.6000503@hardwarefreak.com> (sfid-20120805_153826_573731_00E594B5) <201208051549.22830.Martin@lichtvoll.de> In-Reply-To: <201208051549.22830.Martin@lichtvoll.de> Reply-To: stan@hardwarefreak.com List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Martin Steigerwald Cc: xfs@oss.sgi.com, Eric Sandeen , Stefan Priebe - Profihost AG On 8/5/2012 8:49 AM, Martin Steigerwald wrote: > Am Sonntag, 5. August 2012 schrieb Stan Hoeppner: >> On 8/5/2012 6:03 AM, Martin Steigerwald wrote: >>> Well the default was 16 AGs for volumes < 2 TiB AFAIR. And it has >>> been reduced to 4 for as I remember exactly performance reasons. Too >>> many AGs on a single device can incur too much parallelity. Thats at >>> least is what I have understood back then. >> >> For striped md/RAID or LVM volumes mkfs.xfs will create 16 AGs by >> default because it reads the configuration and finds a striped volume. >> The theory here is that more AGs offers better performance in the >> average case on a striped volume. >> >> With hardware RAID or a single drive, or any storage configuration for >> which mkfs.xfs is unable to query the parameters, mkfs.xfs creates 4 >> AGs by default. The 4 AG default has been with us for a very long >> time. It was never reduced. > = > That does not match my memory, but I=B4d have to look it up. Maybe next = > week. > = > I am pretty sure mkfs.xfs on a single partition on a single harddisk upto = > 2 TiB used 16 AGs for quite some time and now uses 4 AGs since quite some = > time already. I think I have noted the exact xfsprogs version where it wa= s = > changed in my training slides. >>From 'man mkfs.xfs' of xfsprogs 3.1.4 (probably not the latest) "The data section of the filesystem is divided into _value_ allocation groups (default value is scaled automatically based on the underlying device size)." It's not stated in man but the minimum is 4 AGs, unless that has changed in the last couple of years. This is what I was referring to previously when I stated 4 AGs is the default. What you likely did was format a 2TB device and saw 16 AGs due to the automatic scaling, then shortly thereafter formatted a much smaller device and saw the default minimum 4 AGs. Assuming agcount was statically defined, you assumed the default value had been decreased. -- = Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs