-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Awesome! Thanks for the info! Gilbert On 12-01-11 6:04 PM, NeilBrown wrote: > On Wed, 11 Jan 2012 11:01:33 -0500 Gilbert Kowarzyk > <kowarzyk@xxxxxxxxxxxxxx> wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > >> Hello, > >>>> Why do we have these choices, and when should each be used? >>> >>> 1.0 (at the end) is best for RAID1 when booting from the device >>> as the boot-load just doesn't see the RAID at all. >>> >>> 1.1 (at the start) is generally good because various different >>> things have metadata at the start, so there is no chance of >>> confusion about what is using that devices - each possible >>> users will overwrite the metadata of the others. It is also >>> easier to make the devices larger if you don't need to move the >>> metadata. >>> >>> 1.2 (4K from the start) has most of the benefits for 1.1 but >>> works for booting with newer boot loaders - they still want >>> sector 0 for a boot sector but understand the md superblock. > >> I see. Makes also loads of sense. > >> I had two more quick questions: > >> 1.- when would one want to turn off bitmaps? I turned them on, >> but I haven't found why one may want them off (or for what they >> should be turned off). > > There can be a performance impact - writes can be a bit slower with > bitmaps. If that is more important to you that resync speed after a > crash you might turn them off. To change the chunk-size of the > bitmap you need to turn them off, then on again. If you want to > reshape the array you currently need to turn the bitmap off first > (because the bitmap doesn't automatically resize). You turn the > bitmap off with mdadm --grow /dev/mdXX --bitmap=none > > >> 2.- if I ever have a mismatch_cnt different than zero, how would >> I go about finding which drive has the correct info, which was >> the one that got corrupted, and how to obtain the correct one? > > "correct" is not a well defined concept here. > >> In the past I've changed the "CHECK" to "REPAIR" in the >> configuration script that checks the RAID arrays periodically >> (/etc/sysconfig/raid-check), but from what I understood it's a >> bit of luck which one the automatic script will choose out of the >> two drives (assuming raid1). Should I let it be automatic (with >> "repair"), and if not (if I have to check which one is correct >> manually), where could I find information to read about how to do >> this (I am assuming the answer may be long)? > > This: http://neil.brown.name/blog/20100211050355 touches on the > topic ... and is long. > > > NeilBrown -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (Darwin) Comment: digital signature Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk8OJIsACgkQOYVp1RpLsmUE5QCfduzOuF9EPCJoUbXWsq0kYhZF OioAnichYkAyv8r1VLdcMoDSU2aiGF0Q =44rt -----END PGP SIGNATURE----- -- 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
