gharris999;596934 Wrote: > Thanks for the advice so far, but I think I need something a little more > noob-esque. > > After spending a lot of time googling softraid 5 info, I'm still > uninformed. A lot of the info is either contradictory or assumes that > you're using gui tools. I did all of this a few years ago on this same > box using fedora 7 and 4 500gig disks. I obviously didn't retain the > recipe I worked up back then. > > So: the questions I need answered: > > 1). Most of the documentation I'm seeing says to partition the physical > disks...i.e. not to create the raid on the devices themselves..i.e. > use: > > # mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sdb1 > /dev/sdc1 /dev/sdd1 /dev/sde1 > > ..rather than > > # mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sdb /dev/sdc > /dev/sdd /dev/sde > > Why? >
Probably because the kernel will not autodetect RAID setups from the disks themselves. Also if you made the RAID right on the disk, you would be overwriting the MBR, which might confuse the BIOS. Generally it's not "natural" to put anything other then a partition table at the start of a disk. > > > 2). Assuming that the answer to #1 is "because of some important > reason", what is the correct way to partition the 4 physical disks: > fdisk? gdisk? ..and with a 2T disks: MBR? GPT? > You can use MBR upto 2TB. My setup is 4 x 2TB WD greens in software RAID 5 and I use MBR partitioning with fdisk. But GPT via parted would work just as well on modern kernels. > > 3). What is the correct partition type to select? fd00? > fd here. This is only needed by the kernel autodetect code AFAIK. > > 4). Once the drives are partitioned, do they need a file system on > them..i.e. do they need to be formatted before using mdadm --create? > If yes, why? And if yes, which filesystem and what options? > No filesysem is needed. Physical disks -> partitions -> (RAID glue) -> block device -> filesystem is the general order of play. FWIW, it's best to avoid words like "format" in Unix; it's confusing. > > 5). Once the disks are prepared and mdadm starts to create the device, > is it reasonable to expect that mdadm will take up to 20 hours? This is > what mdstat is telling me: > > > Code: -------------------- > > > cat /proc/mdstat > Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] > md0 : active raid5 sde1[4] sdd1[2] sdc1[1] sdb1[0] > 5860543296 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_] > [>....................] recovery = 0.7% (15141256/1953514432) finish=1128.7min speed=28620K/sec > -------------------- > > > This is reasonable for RAID5s in the terabye range. I think my 5.4T RAID took about a day and a half to sync. But then my machine is not a high spec - Ghz VIA with SIL 3114 PCI SATA card. > > 6). After mdadm --create has finished, again, what is the best > filesystem to put on the /dev/md0 device for my purposes. ext4, as > SuperQ suggests above? FWIW, you can mkfs before the sync has finished. You can even fill it up. But this will of course delay the syncing. For good measure I recommend you mkfs then leave the sync to finish, before filling up the RAID with 1GB files (will take a LONG time). Then read he files back. This will verify the disks, primarily. I am still running Debian lenny which does not yet have ext4, and am using ext3 on my 5.4T array (heaven help me if I ever have to fsck). I would go for ext4 if your kernel has the option. Hopefully Debian squeeze will be out soon so I can migrate. :) Good luck and let us you know how you get on. -- Aslak3 (SB 2, SB Boom, SB Radio) ------------------------------------------------------------------------ Aslak3's Profile: http://forums.slimdevices.com/member.php?userid=31977 View this thread: http://forums.slimdevices.com/showthread.php?t=84125 _______________________________________________ unix mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/unix
