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Old 02-09-2007, 01:56 PM   #1
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Software Raid 5, whole disk or partition?

I set up a Raid 5 with three disks. The stats are attached below. I just can't remember, how exactly I set up the array, but i noticed as can be seen below, that the whole drives /dev/sd[abc] are members, and not any particular partitions on them.

What is the difference of having partitions (one for each whole drive) or the whole disk in the array?

fdisk shows 0xfd partitions for /dev/sd[bc] and no partition table for /dev/sda.


Version : 00.90.03
Creation Time : Sat Jan 27 10:15:43 2007
Raid Level : raid5
Array Size : 781422592 (745.22 GiB 800.18 GB)
Used Dev Size : 390711296 (372.61 GiB 400.09 GB)
Raid Devices : 3
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Fri Feb 9 06:24:52 2007
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 64K

UUID : a2df9540:a3801209:3f5460bd:d7d09ba0
Events : 0.312149

Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 32 1 active sync /dev/sdc
2 8 16 2 active sync /dev/sdb

/etc/mdadm/mdadm.conf looks like:
DEVICE partitions
ARRAY /dev/.static/dev/md0 level=raid5 num-devices=3 UUID=a2df9540:a3801209:3f5460bd:d7d09ba0
Old 02-10-2007, 03:43 PM   #2
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There's no difference between a single partition and the whole drive. People use partitions when they have only some partitions in the array. For example, a four drive RAID-5 array (sda1, sdb1, sdc1, sdd1) can also have two RAID-1 arrays (sda2+sdb2, sdc2+sdd2). The RAID-1 arrays can be used for /boot and swap (for example). If you only want all the space on all the drives to be used for the RAID-5 array, you don't need to partition.


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