When buying a FBWC storage controller such as HP's P420, you can choose either a 512MB, 1G, or 2G capacity. What differences do these capacity sizes provide? Is there a metric I can use to choose between them?
Is it related to an 'all-the-time' throughput performance statistic or is it more related to the 'time-of-failure' file size statistic?
I'm trying to understand some SAN infrastructure and I was hoping some of you with more experience than me could help me understand scaling with a SAN.
Imagine that you have some computer servers that have a HBA. They connect either directly or via a switch to a SAN Controller. The SAN Controller then provides one or more LUNs which are mapped to most likely a RAID array on a storage device.
So if I understand correctly, the "controller" represents a performance bottleneck. If you need lots of performance then you add more controllers with connections to their own storage, which then get mapped to the servers that need them.
I imagine you can get some very high performance controllers with huge storage capacities and lower performance controllers with a lower maximum performance? But if you have a switch you can then add several lower performance controllers to your network as you need them?
Please tear apart my understanding if I have it wrong, but I'm trying to work out how you connect HBAs from a server to storage without the fabric simply representing "magic".
I'm in a situation where I'm trying to help out a friend who has little knowledge of his system. He is trying to install a program onto his domain controller and it gives an error stating that it cannot be installed on a RODC. This is the only DC that he has so I am assuming it is not a RODC. Is there a specific way I can have him determine what kind of server this was loaded as? I had him send me a dcdiag /v printout, but I couldn't determine one way or another if it was read only or not.
I know that SAS drives cannot operate on a SATA controller. I know that SATA drives can operate on a SAS controller.
But can Near-Line SAS drives, being SATA drives with a SAS controller, be used on
A) only SAS controllers
B) both SATA and SAS controllers
?
Note that the nearline SAS drives feature "dual port", but I'm unsure if this means "has a SATA and a SAS port" or "has 2 SAS ports". Especially since I seem to read that the connnectors and cables themselves seem to be interchangeable, which, if they are, would make the dual port conundrum moot.
I am wondering what's the purpose of a BBU. My first understanding was, that it enables the cache to write the data to the disc during a power failure. But some specifications say that a BBU can hold its data for up to 72h. I'd expect the data to be written to the disc within milliseconds (given, that the disc still has power, too).
So should a BBU not just protect the cache, but the whole disc for some seconds, too? Wouldn't that be even more secure, because the cache data is written to the disc instead of being around in the cache and waiting for power again? After a second or so, the disc could be shut down.