On Wed, Jan 21, 2009 at 08:14:52PM +0100, Piergiorgio Sartor wrote: > 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? I leave this to others to answer this one. I think it is strange for --detail to report "spares=1" if it is syncing. > [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. I have not tested it. So yes, I think this is something to do a performance test on. I think it should not matter much whether it is in the beginning or in the end. However, if you make a test, then you most likely will do it on a newly created raid, and then files would tend to be allocated in the beginning of the file system, thus favouring a metadata block in the beginning of the raid. In real operation this will tend to even out. Another issue is that the sectors in the beginning of a disk are much faster, a factor of two perhaps, than the sectors in the end of the drive. > 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). mdasseble is specifically made for initrd, so why not use it here? Best regards keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
