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This is a little risky task I want to try. I have a 4 SATA III disks RAID10 array running on LSI (former 3ware) 9750-8i controller with BBU (read and write cache enabled). In case of hardware failure I would like to move the array to older 3ware controller, model 9650SE-8LPML without BBU.

Configuration of that array is:

/c2/u0 status = OK
/c2/u0 is not rebuilding, its current state is OK
/c2/u0 is not verifying, its current state is OK
/c2/u0 is initialized.
/c2/u0 Write Cache = on
/c2/u0 Read Cache = Intelligent
/c2/u0 volume(s) = 1
/c2/u0 name = mons                 
/c2/u0 serial number = S1DGCBEB159EED0051BF 
/c2/u0 Ignore ECC policy = off       
/c2/u0 Auto Verify Policy = on        
/c2/u0 Storsave Policy = balance     
/c2/u0 Command Queuing Policy = on        
/c2/u0 Rapid RAID Recovery setting = all
  1. Is this at all possible?
  2. Is the lack of BBU in the older controller will not cause failure?
  3. In such a case (no BBU), only the read and write cache stops working?
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Are you essentially asking if the hardware is sufficiently compatible that you can use the 9650 on an array built on the 9750? If so, I have to wonder at your valuation of your data as valuable enough to protect with RAID10, but worth less than a backup 9750 adapter card. – Slartibartfast Mar 19 '14 at 4:52
Yes, the essential question is about the hardware. Please do not wonder and worry about my data and it's value ;) – Scyld de Fraud Mar 19 '14 at 20:45
up vote 1 down vote accepted

I tested this a long while ago when we upgraded from 9650SE/9690SA to 9750-4i and 9750-8i: - moving RAID arrays created on 9650 to 9750 works fine - moving RAID arrays created on 9750 to 9650 works fine - moving a degraded array from 9750 to 9650 works fine - moving a degraded array from 9750 to 9650 in the middle of a rebuild just continues rebuilding on the 9650

Conclusion: 9650 and 9750 are compatible in both ways. Only difference is the required drivers.

I tested using 6x Seagate 7200.11 500GB and RAID6. Other RAID levels could give different results, but I think that if RAID6 works, you should be fine on other RAID levels too.

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I have an answer from other source:

«You can do this, and both controllers should be able to see the RAID configs without any issues. Just make sure you update the 9650SE to the latest available firmware. There is little risk to the data without a BBU unless there is a power outage, but you are correct, write back will be disabled. Adding a BBU later will allow to set the write back policy without needing to reconfigure anything.»


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