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Mickys21
n00b
Joined: 22 Jul 2003
Posts: 61
Location: Ipswich, UK
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 Posted: Thu Jun 17, 2004 2:53 pm Post subject: RAID Trouble |
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Set Up a RAID 5..
9.1g - Boot Partition sda1 -- Swap sda2 -- / sda3
9.1g - / sdb1
9.1g - / sdc1 (Spare Disk)
Seemed to be set up well...
lsraid gives me....
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[dev 9, 2] /dev/md2 8CE3C5A5.7FBE3A36.3989A6A7.6CB1410E online
[dev 8, 3] /dev/sda3 8CE3C5A5.7FBE3A36.3989A6A7.6CB1410E good
[dev 8, 17] /dev/sdb1 8CE3C5A5.7FBE3A36.3989A6A7.6CB1410E good
[dev 8, 33] /dev/sdc1 8CE3C5A5.7FBE3A36.3989A6A7.6CB1410E spare
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Looks fine to me
also cat /proc/mdstat gives me
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Personalities : [linear] [raid0] [raid1] [raid5] [multipath]
md2 : active raid5 sdc1[2] sdb1[1] sda3[0]
8305536 blocks level 5, 32k chunk, algorithm 3 [2/2] [UU]
unused devices: <none>
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again looks fine to me.
but on doing a 'df' command it shows /dev/md2 only to have 8.5gb of space, identical to /dev/sda, it isnt showing the combind space of sda3 and sdb1
any ideas why this is not correct..
my /etc/raidtab
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raiddev /dev/md2
raid-level 5
nr-raid-disks 2
nr-spare-disks 1
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda3
raid-disk 0
device /dev/sdb1
raid-disk 1
device /dev/sdc1
spare-disk 0
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its baffling me at the moment as everything looks fine, but I should have 16gb of space and not the 8.5 its giving me. |
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kiezpro
Tux's lil' helper
Joined: 13 May 2004
Posts: 126
Location: Yes
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| Posted: Thu Jun 17, 2004 5:20 pm Post subject: |
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AFAIK, for a RAID 5 to make sense you need at least three disks in the array, as the capacity of the array is n-1, where n is the total number of disks. So, if you set up your raidtab like this:
| Code: | raiddev /dev/md2
raid-level 5
nr-raid-disks 3
nr-spare-disks 0
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda3
raid-disk 0
device /dev/sdb1
raid-disk 1
device /dev/sdc1
raid-disk 2 |
you should have what you want. If you want to have a hot spare disk, you'll have to add another one.
Please be aware of the fact that you'll have to rebuild the array and thus lose all data on the array if you change the raidtab. |
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