So what you want to do is have 3 partitions where you have /, /boot & the rest? For desktop usage it's OK to use that setup since you won't be writing to / and the other segments a lot at the same time. If you're running an application which writes a lot of data to / and you require to read/write a lot of data of the rest of the disk, it will conflict and slow things down a lot. Basically, you're partitioning each disk and making each partition belong to an array. So if the collective partitions of Array1 are busy with something and the partitions of Array2 are also busy, you'll slow down because you're reading/writing to/from the same disk from two different partitions. On Tue, Oct 13, 2009 at 4:13 PM, Antonio Perez <ap23563m@xxxxxxx> wrote: > If I'm posting to the wrong group, sorry. just point to the RTFM link. > > This post is about setting up a Debian box with four disks (size should not > be important, me thinks), let's assume that a Raid 5 is the correct type for > the intended use. > > Keeping aside LVM and/or layering of md (just for simplicity), and taking > into account that /boot, / and maybe other areas should go in a Raid 1 > configuration, for booting reliability. I have three questions that perhaps > you could help to clarify: > > 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. > > Setting the whole disk as one partition would prevent any conflict but would > take longer to rebuild and files would be spread over the whole area of the > disk. > > I really don't know the internals of md well enough to tell what advantages > and problems one setup has over the other. > > 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? > > 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? > > TIA > > -- > Antonio Perez > > -- > 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 > -- Majed B. -- 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
