From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Hofman Subject: Re: Rotating RAID 1 Date: Sun, 11 Sep 2011 21:21:27 +0200 Message-ID: <4E6D0A37.2000900@ivitera.com> References: <4E497FB5.3030109@ivitera.com> <4E49849E.4030604@ivitera.com> <20110816084251.2d8e7831@notabene.brown> <20110816095517.757afc07@notabene.brown> <4E4A0F86.6010907@ivitera.com> <4E6A9328.6070801@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4E6A9328.6070801@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: Bill Davidsen Cc: linux-raid List-Id: linux-raid.ids Dne 10.9.2011 00:28, Bill Davidsen napsal(a): > Pavel Hofman wrote: >> Dne 16.8.2011 01:55, NeilBrown napsal(a): >> >>> Also, it doesn't have to be a linear stack. It could be a binary tree >>> though that might take a little more care to construct. >>> >> Since our backup server being a critical resource needs redundancy >> itself, we are running two degraded RAID1s in parallel, using two >> internal drives. The two alternating external drives plug into the >> corresponding bitmap-enabled RAID1. >> > > I wonder if you could use a four device raid1 here, two drives > permanently installed and two being added one at a time to the array. > That gives you internal redundancy and recent backups as well. I am not sure you could employ the write-intent bitmap then. And the bitmap makes the backup considerably faster. > > I'm still a bit puzzled about the idea of rsync being too much CPU > overhead, but I'll pass on that. The issue I have had with raid1 for a > backup is that the data isn't always in a logical useful state when you > do physical backup. Do thing with scripts and hope you always run the > right one. I am afraid I do not understand exactly what you mean :-) We have a few scripts, but only one is started manually, the rest is taken care of automatically. Pavel.