On Sat, 13 Oct 2007, Marko Berg wrote:

Bill Davidsen wrote:

quoted

Marko Berg wrote:

quoted

I added a fourth drive to a RAID 5 array. After some complications related 
to adding a new HD controller at the same time, and thus changing some 
device names, I re-created the array and got it working (in the sense 
"nothing degraded"). But size results are weird. Each component partition 
is 320 G, does anyone have an explanation for the "Used Dev Size" field 
value below? The 960 G total size is as it should be, but in practice 
Linux reports the array only having 625,019,608 blocks.

I don't see that number below, what command reported this?

For instance df:

$ df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/md0             625019608 358223356 235539408  61% /usr/pub

quoted

quoted

How can this be, even though the array should be clean with 4 active 
devices?

$  mdadm -D /dev/md0
/dev/md0:
       Version : 01.02.03
 Creation Time : Sat Oct 13 01:25:26 2007
    Raid Level : raid5
    Array Size : 937705344 (894.27 GiB 960.21 GB)
 Used Dev Size : 625136896 (298.09 GiB 320.07 GB)
  Raid Devices : 4
 Total Devices : 4
Preferred Minor : 0
   Persistence : Superblock is persistent

   Update Time : Sat Oct 13 05:11:38 2007
         State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
 Spare Devices : 0

        Layout : left-symmetric
    Chunk Size : 64K

          Name : 0
          UUID : 9bf903f8:7fc9eec1:2ff25011:37e9607b
        Events : 2

   Number   Major   Minor   RaidDevice State
      0     253        2        0      active sync 
/dev/VolGroup01/LogVol02
      1       8       33        1      active sync   /dev/sdc1
      2       8       49        2      active sync   /dev/sdd1
      3       8       17        3      active sync   /dev/sdb1


Results for mdadm -E <partition> on all devices appear like this one, with 
positions changed:

$ mdadm -E /dev/sdc1
/dev/sdc1:
         Magic : a92b4efc
       Version : 1.2
   Feature Map : 0x0
    Array UUID : 9bf903f8:7fc9eec1:2ff25011:37e9607b
          Name : 0
 Creation Time : Sat Oct 13 01:25:26 2007
    Raid Level : raid5
  Raid Devices : 4

 Used Dev Size : 625137010 (298.09 GiB 320.07 GB)
    Array Size : 1875410688 (894.27 GiB 960.21 GB)
     Used Size : 625136896 (298.09 GiB 320.07 GB)
   Data Offset : 272 sectors
  Super Offset : 8 sectors
         State : clean
   Device UUID : 9b2037fb:231a8ebf:1aaa5577:140795cc

   Update Time : Sat Oct 13 10:56:02 2007
      Checksum : c729f5a1 - correct
        Events : 2

        Layout : left-symmetric
    Chunk Size : 64K

   Array Slot : 1 (0, 1, 2, 3)
  Array State : uUuu


Particularly, "Used Dev Size" and "Used Size" report an amount twice the 
size of the partition (and device). Array size is here twice the actual 
size, even though shown correctly within parentheses.

Sectors are 512 bytes.

So "Used Dev Size" above uses sector size, while "Array Size" uses 1k blocks? 
I'm pretty sure, though, that previously "Used Dev Size" was in 1k blocks 
too. That's also what most of the examples in the net seem to have.

quoted

quoted

Finally, mdstat shows the block count as it should be.

$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdb1[3] sdd1[2] sdc1[1] dm-2[0]
     937705344 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] 
[UUUU]
    unused devices: <none>


Any suggestions on how to fix this, or what to investigate next, would be 
appreciated!

I'm not sure what you're trying to "fix" here, everything you posted looks 
sane.

I'm trying to find the missing 300 GB that, as df reports, are not available. 
I ought to have a 900 GB array, consisting of four 300 GB devices, while only 
600 GB are available. Adding the fourth device didn't increase the capacity 
of the array (visible, at least). E.g. fdisk reports the array size to be 900 
G, but df still claims 600 capacity. Any clues why?

-- 
Marko
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You have to expand the filesystem.