about linear and about RAID10 (was "Re: how do i fix these RAID5 arrays?")

[David T-G <davidtg-robot@justpickone.org>]

Wol, et al --

...and then Wol said...
% On 24/11/2022 21:10, David T-G wrote:
% > How is linear different from RAID0?  I took a quick look but don't quite
% > know what I'm reading.  If that's better then, hey, I'd try it (or at
% > least learn more).
% 
% Linear tacks one drive on to the end of another. Raid-0 stripes across all
% drives. Both effectively combine a bunch of drives into one big drive.

Ahhhhh...  I gotcha.  Thanks.


% 
...
% 
% That's why there's raid-10. Note that outside of Linux (and often inside)
% when people say "raid-10" they actually mean "raid 1+0". That's two striped
% raid-0's, mirrored.

That's basically what I have on the web server:

  jpo:~ # mdadm -D /dev/md41 | egrep '/dev|Level'
  /dev/md41:
	  Raid Level : raid1
	 0       8       17        0      active sync   /dev/sdb1
	 1       8       34        1      active sync   /dev/sdc2
  jpo:~ # mdadm -D /dev/md42 | egrep '/dev|Level'
  /dev/md42:
	  Raid Level : raid1
	 0       8       18        0      active sync   /dev/sdb2
	 1       8       33        1      active sync   /dev/sdc1
  jpo:~ # mdadm -D /dev/md40 | egrep '/dev|Level'
  /dev/md40:
	  Raid Level : raid0
	 0       9       41        0      active sync   /dev/md/md41
	 1       9       42        1      active sync   /dev/md/md42
  jpo:~ #
  jpo:~ #
  jpo:~ # parted /dev/sdb p
  Model: ATA ST4000VN008-2DR1 (scsi)
  Disk /dev/sdb: 4001GB
  Sector size (logical/physical): 512B/4096B
  Partition Table: gpt
  Disk Flags:
  
  Number  Start   End     Size    File system  Name                    Flags
   1      1049kB  2000GB  2000GB               Raid1-1
   2      2000GB  4001GB  2000GB               Raid1-2
   4      4001GB  4001GB  860kB   ext2         Seag4000-ZDHB2X37-ext2
  
  jpo:~ # parted /dev/sdc p
  Model: ATA ST4000VN008-2DR1 (scsi)
  Disk /dev/sdc: 4001GB
  Sector size (logical/physical): 512B/4096B
  Partition Table: gpt
  Disk Flags:
  
  Number  Start   End     Size    File system  Name                    Flags
   1      1049kB  2000GB  2000GB               Raid1-2
   2      2000GB  4001GB  2000GB               Raid1-1
   4      4001GB  4001GB  860kB                Seag4000-ZDHBKZTG-ext2


% 
...
% 
% Either version (10, or 1+0), gives you get the speed of striping, and the
% safety of a mirror. 10, however, can use an odd number of disks, and disks
% of random sizes.

That's still magic to me :-)  Mirroring (but not doubling up the
redundancy) on an odd number of disks?!?


% 
% Cheers,
% Wol


HAND

:-D
-- 
David T-G
See http://justpickone.org/davidtg/email/
See http://justpickone.org/davidtg/tofu.txt