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I have a system with pre configured hardware RAID. It has 2 disks in a RAID1 configuration. It has a further 6 disks in a RAID5 configuration. The 6 disk RAID5 is split (by the hardware) to look like 2 separate disks:

/dev/sda - RAID1 2x discs
/dev/sdb - RAID5 6x discs (half of each disk)
/dev/sdc - RAID5 6x discs (half of each disk)

I have an lvm physical volume for each of the above. I am considering adding PV /dev/sda and PV /dev/sdb, and possibly /dev/sdc to the same volume group.

To my naive view of LVM/RAID, this is looks like logical volumes would be backed by a mixture of RAID5 and RAID1. What are the risks, ineffciencies or management difficulties with this approach ?

Thanks,

Rob

  • What type of RAID controller is this? – ewwhite Sep 8 '14 at 11:45
  • I have it listed as "LSI9260-8i" lsi.com/products/raid-controllers/pages/… – Robin Bryce Sep 8 '14 at 12:04
  • Also, I meant 6 disks in RAID 5 not 4 ! Thanks. – Robin Bryce Sep 8 '14 at 12:04
  • Do you have any ability to change the hardware RAID configuration? – ewwhite Sep 8 '14 at 12:06
  • Not in this instance. But for subsequent projects possibly. – Robin Bryce Sep 8 '14 at 12:57
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I would not suggest doing this, especially combining virtual disks (hardware) into a single volume group under LVM without knowing the exact composition of the virtual disks. This will have implications with:

  • Redundancy - What would be the impact of a failed disk be? E.g. a failure of disk #5 will compromise DG's 2 and 3.
  • Performance - Performance on a 2-disk mirror will have a different profile than a 6-disk RAID5. You won't have any control over where your data is.
  • Supportability - It sounds like a messed-up configuration. I wouldn't want to inherit it. If you have an option to change things, you should.
  • Excellent. Thankyou very much – Robin Bryce Sep 8 '14 at 13:32

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