From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: how to synchronize two devices (RAID-1, but not really?) Date: Tue, 15 May 2007 11:44:34 +0200 Message-ID: <46498102.6030005@wpkg.org> References: <4649760A.1060805@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Gordon Henderson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Gordon Henderson schrieb: > On Tue, 15 May 2007, Tomasz Chmielewski wrote: > >> I have a RAID-10 setup of four 400 GB HDDs. As the data grows by >> several GBs a day, I want to migrate it somehow to RAID-5 on separate >> disks in a separate machine. >> >> Which would be easy, if I didn't have to do it online, without >> stopping any services. >> >> >> M1 - machine 1, RAID-10 >> M2 - machine 2, RAID-5 >> >> >> My first idea was to copy the data with rsync two or three times >> (because the files change, I would stop the services for the last run) >> - which turned out to be totally unrealistic - I started rsync process >> two days ago, and it still calculates files to be copied (over 100 >> million files, with hardlinks etc.). > > I have recent experience of copying up to 1TB parititions to offsite > backup servers via rsync (and a 10Mb line), and it can be done. > > You do need a recent version of rsync and a lot of memory in both > servers. I'm really surprised it takes days to do this on your server - > although maybe the source server really is busy? Yes, the server is really busy and reads/writes a lot - that's one. Two, it's being done over iSCSI in a pretty complicated scenario: 100 Mbit M1 (RAID-10 storage) <--> very busy virtual machine in Xen / / 1 Gbit / machine with rsync process <--> M2 (RAID-5 storage) 1 Gbit So there is a slow point of just 100 Mbit to access the storage, which is normally fully filled anyway. rsync, even 3.0, just doesn't fit here - it has to be done in sort of a "mirror" way. -- Tomasz Chmielewski htp://wpkg.org