From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Leslie Rhorer" Subject: RE: Write intent bitmaps Date: Sun, 28 Jun 2009 13:14:23 -0500 Message-ID: <20090628181428746.EXYX19511@cdptpa-omta03.mail.rr.com> References: <19002.62697.475588.28776@notabene.brown> Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <19002.62697.475588.28776@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: 'Neil Brown' , 'Carlos Carvalho' Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids > > >5. What happens if the bitmap is lost or the external drive fills up? > > > > No idea. > > If the bitmap is lost, it is just as though you didn't have a bitmap > (or as though all the bits in the bitmap were set to one). OK, what about the thread in this list where (as I recall) the fellow's bitmap was corrupted or lost and it evidently caused the entire array to go splat? That's worrisome. > The drive filling up is not relevant. When the bitmap is in a > separate file, the file is preallocated to be the right size. Let me take a little different tack. I don't have any ext2 or ext3 file systems on the server. If I am going to set up an external bitmap, I am going to have to steal some space from one of the other file systems - perhaps from the swap area (5G), the boot file system (reiserfs - 109G), or the Windows XP filesystem (NTFS - 40G). I need to be able to calculate how much space to steal to fit the bitmap, and allow for later expansion. > > >If so, would ext2 probably be the best choice? > > > > That's what the man page says. I find it strange since if it's a file > > the filesystem shouldn't matter. Neil? > > The way that md writes to the bitmap file is not entirely portable > across different filesystems. As the man page say, it is known to > work for ext2 and ext3. Either is a fine choice. I'm fine with shrinking one of the existing file systems and creating a tiny partition just for the bitmap.