On Tue Oct 13, 2009 at 09:13:13AM -0400, Antonio Perez wrote: > 1.- Should the "rest of the disk" be only one partition? > I have read that making several partitions and setting several md disks: > sd[a..d]2 --> md1 > sd[a..d]3 --> md2 > sd[a..d]4 --> md3 > would help with the rebuild time of each md, which sounds correct. It is > also proposed that the md on the outer area of the disk would be faster > allowing for better control of performance, assigning faster mds to the more > used filesystems. > > However, and this I don't know, those sda[2..4] are not really different > devices (spindles) and reads to one md would conflict (or not?) with reads > to the other mds. > Any reads to the same disk will conflict - whether they're on separate arrays or within a single array shouldn't make any difference (the IO elevator is set on the disk rather than the array, so I assume it will gather requests across all arrays). md itself knows that the arrays share disks, so will ensure any maintenance tasks (resyncs, etc) only run on a single array at a time. > 2.- On the Raid 1: How many sectors to copy? 63? > On an update of grub code, core.img could change, which means that the first > 63 sectors (to be on the safe side) of the disk which gets the update should > be copied to the other 3 disks. > Or is it that the md code would mirror sectors 1-62 and only the MBR needs > to be manually mirroed? > Not sure what you mean here. If you have /boot on a RAID1 array then it's mirrored, so the stage1.5 and stage2 bootloaders get mirrored via that. The stage1 bootloader is usually installed into the MBR, so only that needs replicating separately. > 2.- Is there a recomended way to trigger the said copy of question 2? > Where should a call to copy the MBR should be placed? On update-grub? > I always just rerun the grub install for each disk manually (see http://lists.us.dell.com/pipermail/linux-poweredge/2003-July/008898.html for example). Automating it will depend on your distribution - if update-grub is what's called after a grub update (and it isn't overwritten by the update) then this would seem the logical place to do it. HTH, Robin -- ___ ( ' } | Robin Hill <robin@xxxxxxxxxxxxxxx> | / / ) | Little Jim says .... | // !! | "He fallen in de water !!" |
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