From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Keene Subject: Re: mdadm raid5 with lvm: advantages? Date: Tue, 11 Jan 2011 12:58:02 -0600 (CST) Message-ID: References: <4D2CA32E.3030303@gmail.com> <20110111234945.7c601067@natsu> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <20110111234945.7c601067@natsu> Sender: linux-raid-owner@vger.kernel.org To: Roman Mamedov Cc: Zdenek Kaspar , Richard Grundy , linux-raid@vger.kernel.org List-Id: linux-raid.ids Roman, LVM supports both sparse LVs (--virtualsize) and defragmentation (though as you say it's not currently easy -- I started writing a script to handle it but it's not a big enough problem that I've ever actually wanted to use the script, still a general purpose "lvdefrag" could be written). Thanks, Roy Keene On Tue, 11 Jan 2011, Roman Mamedov wrote: > On Tue, 11 Jan 2011 19:36:30 +0100 > Zdenek Kaspar wrote: > >> It makes sense to use LVM for virtualization and iSCSI to get rid of big >> file images (unwanted fs overhead/fragmentation). But yes, in some use >> cases this is OK. > > Since you mentioned fragmentation - there are ways to both make sparse file > images, and to defragment them when needed (on some filesystems like XFS and > btrfs). But when using LVM instead of file images, the user has neither: LVM > can't have sparse LVs, and it can't (easily) defragment an LV that is > fragmented over one or several PVs. Or am I missing something here? > > -- > With respect, > Roman >