cache on msa1000

[Mike Gentles]

I have some confusion about how the cache operates on the msa1000.

Is there mirrored cache?? And if so, is it only internal to each controller (dimm to dimm mirror) or is it controller to controller mirroring??

I ask because what happens to post-write data in cache when controller dies and the msa failsover to the standby controller?? Is the data lost? Is the contents of the active cache mirrored over to the standby controller over the ICL during normal operation? If the data is stuck in the cache I can see removing the cache and sticking it on standby (new active) controller to get the data to be written down to the drives (assuming done before the batteries discarge). This would require bringing down the MSA for approx 2-3 mins. Not good.

Can someone help me out with the cache function as far as mirroring goes.

Thanks in advance,

Mike Gentles

[david5337_1]

As I know,the two controller has the mirror cache,share all data and configuration infomation.
When one controller fail,other controller can find the infomation,so it can hand all data.
So if the cache has some data owen by other fail controller;the goog controller will manage the data.
Thanks

[Mike Naime]

Mike, I think that you are going to have to ask an HP rep about this. The manual doesn't mention anything about how the Cache RAM works/functions. It tells you how to replace the failed dimms, but not how it is supposed to function.

[Mike Gentles]

David,

I had actually since tested things out and found what you said to be true. But I do thank you for your response. It only makes sense that the config/data in cache is mirrored over, I just havent been able to prove it via documentation.

Mike

[vofsky]

Hi David,
According to you,the size of memory installed in these two controller have to be equal?I mean if one controller has 256M memory ,the other must have 256M.And if not,Can the controller mirror the other one?

[vofsky]

Hi David,
According to you,the size of memory installed in these two controller have to be equal?I mean if one controller has 256M memory ,the other must have 256M.And if not,Can the controller mirror the other one?Is it correct?

[Mike Gentles]

The caches do have to be exactly the same. Not only in total capacity, but also the same modules.

The first rev of the controllers came with a single 128MB module and can be upgraded with one more. If you were to put a second controller in with only 1 module, you would receive a 'cache mismatch' error and would not operate in a redundant fashion..which is the whole point of the second one.

The second rev comes with 256MB module and can upgrade to one more, with all the same rules applying.

Mike

[kubilay husmenoglu]

We have a problem. after applying firmware 4.32 on MSA1000, we see zero disk throughput and zero performance counters on msa1000 disks when flushing cache to disk. Flushing time increases when we increase the write cache ratio until 100%.
we use windows 2003 cluster.
Thanks for any help