From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piergiorgio Sartor Subject: Re: Performance question Date: Wed, 21 Jan 2009 20:14:52 +0100 Message-ID: <20090121191452.GA4752@lazy.lzy> References: <20090117171806.GA9432@lazy.lzy> <20090117220849.GB29866@rap.rap.dk> <20090119181253.GA4290@lazy.lzy> <20090121001503.GA26587@rap.rap.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20090121001503.GA26587@rap.rap.dk> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi again, [--detail vs. --examine] > --detail looks at the running arrays, while --examine most > likely (depending on mdadm.conf) looks at all partitions > on the system. > > Given that the arrays are just created in the installation process, and > the active running arrays are most likely the ones you want your system > to know of, I think --detail is the better. --examine does on two of my > systems generate info that are in conflict and not suitable for a > mdadm.conf file, such as two /dev/md1 with different UUIDs. yes, but I noticed that with "--detail" and an array (RAID-1) resyincing, it reports "spares=1" too, while when the array is in sync, it prints the correct geometry. So, I was wondering, since I also noticed that "--examine" produces the arrays with /dev/md/"name", so if two arrays have same name, it ends up with the same device. Is this maybe a bug of mdadm? [metadata position] > To me it does not matter that much, except for the booting device. > Each partition in the booting device must look like a normal (ext3) > partition, as grub and lilo does not know of raids, and just treats > a booting partition as a standalone partition. So here you should use > 0.90 metadata, which is put at the end of the array. Well, I was a bit mixing up things with this question. In the back of my head the question was: What about performances, RAID-10 f2, bitmap (important) and metadata 1.0 vs. 1.1? This could be a further test for performances. It would be interesting to know if it is better to have the metadata at the beginning or at the end of a RAID-10 f2, with two HDs, having the bitmap enabled. Or if it does not matter at all. Reading around I found different "opinions" about bitmap and performances, but I did not find a "convincing" test. Thanks again. Different item of the wiki, I run into it today. Maybe the "initrd" description could be updated, since it uses "mdassemble", while the "initrd" I have uses directly "mdadm -As --auto=yes ..." (I do not remember the full line). Hope this helps, bye, -- piergiorgio