Using a hardware RAID with BBU

[da123]

Dear Community,

I want to set up a new PVE environment and I´m not sure about the correct caching configuration.

I´m using the Adaptec ASR-71605 hardware RAID controller (RAID 1 and 2x SSD) with an integrated BBU and 1 GB of Cache. What is the best configuration in my case?
If I understand this official guide correctly, I can use cache=writeback.

Should I use Write back or Write back (unsafe)? How unsafe is this configuration if I use a BBU?

I thank you for any help!

Best Regards

 

[LnxBil]

Should I use Write back or Write back (unsafe)? How unsafe is this configuration if I use a BBU?

Those are two different things. What you can choose in the dialog is the cache in your main memory. Use "none" here to have no OS-side cache and just rely on the RAID controller cache. This is the safest option (you will go with it, won't you? Therefore you bought a BBU, right?).

Also be aware of the cache ratio in your raid controller, which splits its memory in read and write cache. The write cache is often only useful for scattered sync writes, which your SSD will handle much better than spinning rust. In modern RAID controllers, the difference in benchmarkable and "feelable" speed is not as big as it would be with harddisks, in which your synchronous, scattered/random write will tremendously perform better.