From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Heinzmann Subject: mdadm 2.2 new option Date: Thu, 15 Dec 2005 23:14:02 +0100 Message-ID: <43A1EAAA.6090802@gmx.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hello, i just downloaded the mdadm 2.2 version. It seems that there are some new options which are not explained in details. of special interest are 2 options. -GROW The new grow mode is very very helpfull for us. It would allow us to do resize operations with md devices at last - without the need for LVM. The manpage states that the GROW mode requires kernel support to work. There is no note that states, which kernel supports the options. Also with various distributions with patched kernels its not possible to say version X.Y.Z. of the kernel contains the required patches. Is there a way to find out via mdadm, if the current kernel supports the GROW mode, prior to performing the GROW ? -bitmap As far as I understand this bitmap options, in incorperates write intend logging. Is this based on paper by James Bottomley ? Also is there a way to find out via mdadm if the running kernel supports intend logging via mdadm ? -There is also an option --write-mostly since 2.0. I guess this especially usefull for MD devices with large storage arrays as backend. They have clever caches and read ahead paramaters, that can be non-effective if we change the disk for each read. Does this option require a kernel modification too ? One last question. Besindes the source code and manpage is there oterh documentation available on how the md works internally ? (update of superblock, handling of device renaming inside the superblock etc.) Thanks, Robert Heinzmann