3ware 9690SA-8i BBU/Write Cache

[nry]

I have been reading and from what I understand, having write cache enabled on a RAID array will increase the write performance to the disks?

If this is correct I need a BBU to enable the write cache (safely)?

Now looking at the prices of these things im sat here
What module do I need as I have found
BBU-MODULE-03
BBU-MODULE-04

I have also found that I can get BBU-MODULE-03 for £14 for the small controller card and £25 for a new battery, which is considerably less than the £90 I found the whole thing for.

Am I heading in the right direction here? Im currently only playing with RAID arrays with a few spare drives to see how they work etc with the intention of creating a 10-16TB array later in the year. Any advice would be brilliant
Thanks

 

[tugaricardo]

I have been reading and from what I understand, having write cache enabled on a RAID array will increase the write performance to the disks?

If this is correct I need a BBU to enable the write cache (safely)?

Now looking at the prices of these things im sat here
What module do I need as I have found
BBU-MODULE-03
BBU-MODULE-04

I have also found that I can get BBU-MODULE-03 for £14 for the small controller card and £25 for a new battery, which is considerably less than the £90 I found the whole thing for.

Am I heading in the right direction here? Im currently only playing with RAID arrays with a few spare drives to see how they work etc with the intention of creating a 10-16TB array later in the year. Any advice would be brilliant

Hello nry are you ok?
I have the same controller with BBU and 2x SSD Corsair F120 attached on it.
1- You should choose the BBU Module 04 because you have oportunity to put the module in other slot, far away of heat of controller. Mine is out of PC Case.
2- You should choose the default settings of controller. I mean, Intelligent Read Ahead cache, other 2 settings on background in adaptative mode and write back cache. With BBU, choose always Balanced Storsave profile. I've seen people on other forums and reviews,has chosed BBU + Performance storsave profile, this is wrong,very wrong because in Performance mode, the BBU never does write journaling, just on Balanced and Protection. The manual says, " on performance mode, this essencially disable the BBU for this unit".
So, the BBU is the right choice for performance improvement.

 

[drescherjm]

If this is correct I need a BBU to enable the write cache (safely)?

Yes. If you do not care about loss during an instant power outage (no UPS) or system crash (if you still see these) then you can turn the write cache on without the BBU.

Without the BBU most hardware raid controllers will switch to write through instead of write back. This will definitely slow down write operations and reduce your random performance.

 

[tugaricardo]

Yes. If you do not care about loss during an instant power outage (no UPS) or system crash (if you still see these) then you can turn the write cache on without the BBU.

Without the BBU most hardware raid controllers will switch to write through instead of write back. This will definitely slow down write operations and reduce your random performance.

Yes and no...
The UPS is not a substitute of BBU. But yes, specifically on 3ware controllers, they allow turn on the cache without BBU. Ironically, the storsave profile in balanced mode with BBU is more speedy than performance mode with and without BBU in certain circumstances,specially on mix read and write operations due to write journaling of BBU and the fact to ignore FUA command