LSI RAID ????

[Bozo]

I recently purchased an Intel RS2WC040 RAID controller. Basically an LSI controller with Intel labels.
When setting up a RAID 0 drive, I found that I cannot change from 'write through' to 'write back'. What's the secret? Googling gave me a lot of non-answers, even more confusion.

Thanks

 

[sdbardwick]

Bad/missing BBU?

To avoid data loss, the RAID firmware will change Write Policy to "Write Through" whenever a backup battery unit is not present or does not have sufficient level of charge. To prevent this from happening you can uncheck "Write Through for failed or missing BBU" option.

Intel source

 

[Bozo]

Thanks! I'll have to look for that check box.

 

[Bozo]

Still haven't found that check box.

 

[sdbardwick]

From my quick reading of the CLI manual(PDF), it looks like the BBU options are tied to the each array, rather than being a global adapter-wide setting. Maybe the checkbox is nested somewhere under array properties.
Look for LDSetProp in the above PDF for more info.

 

[MaxBurn]

Assuming it is similar to the perc6i (also LSI but with dell labels) there is an overide to allow write back cache in the bios setup screens even though there is no bbu attached.

In the dell/lsi software package I can see the status of the cache but don't see a place to overide it.

 

[Bozo]

Still no write back. I believe it's because LSI Advanced features are disabled. It takes a super secret pass-code to be able to register on the LSI site, and then they give you another super secret pass-code to activate the advanced settings. I don't have either.
What a crock of shit.

 

[sdbardwick]

Bummer.
Might as well try to set WB via the CLI (if you haven't already) to see what error code it returns - might give more clues.
Hell, it might just work but I'm doubtful, as no BBU will work with that adapter (according to Intel, BBU functionality is outside the targeted price/performance envelope), I fear that they have permanently disabled WB caching on that model.

 

[Mercutio]

For my M1505, I was able to find a set of instructions for enabling and changing some firmware functions that were disabled with the IBM version of the LSI card.

 

[Bozo]

It looks like the LSI MegaRAID SAS 9240-4i is the same card as the Intel.
Does anyone know if the firmware will allow you to enable 'write back' on the LSI card? On the Intel card I am getting ~9MB/sec writes in a RAID 5 setup.
Do you think it's posible to flash the Intel card with the LSI firmware?

 

[Mercutio]

It looked to me like LSI firmware was pretty well understood by third parties. The bigger issue is that you'd be putting your hardware in a configuration that isn't supported by Intel or LSI, so there is some risk involved with making those changes.

 

[ddrueding]

The other thing to keep in mind is the servers ability to cache writes from network users, the poor local writes might not be that big a deal.