I did not really see this as a "problem" to place in the support queue. It is more a question/statement for the general population.
I have two unRAID machines, both running inside of VMWare off of my ESXi server. One is 4.7 with 3 1TB drives and one is the new 5.0-rc10 with 2 2TB (let me know if you would like to know how I got it working), both appear to be function fine but I keep running into what I think are odd data transfer speed issues.
When checking either system for the displayed transfer rate of the parity check (unRAID Main menu), I will see anywhere from 50MB/sec up to over 100MB/sec. Which seems consistent with the hardware I have installed.
When transferring data to either machine while the parity check is running, transfer speeds will max out at around 15MB/sec and usually drop off after several minutes in to the copy process to something less than that. If I copy files when not running a parity check, then I usually see transfer speeds up in to the 25MB/sec to 40MB/sec range.
If I happen to want to copy files after I have installed a new parity drive, I might as well forget it, because it with either fail outright or slows down to below 1MB/sec and eventually times out on the copy process. Which I guess I can at least understand logically, due to the system diverting most of the processing resources to building the parity drive, but to stop completely, that is ridiculous.
Now, here is my real rub. When running stable and NOT running a parity check, I get my normal 25MB/sec to 40MB/sec transfer speeds. If I completely pull the parity drive out of the configuration and just use it as storage, I will get consistent transfer rates of 60MB/sec to 80MB/sec. Which seems to indicate that the system can get these types of transfer speed and is not being hampered from a hardware or VMWare issue.
WHY SUCH A DISPARATE DIFFERENCE IN TRANSFER SPEEDS? I could see loosing a few MB/sec on the transfers due to the system trying to keep the parity information up to date with what is being transferred to the array. But almost a 50% reduction? I just do not understand that.
Hell, even Microsoft's software raid in Windows server does not slow down that much on data transfers.
So out of all this rambling, my question is, why is it so much slower when the parity is enabled and is there anyway to resolve this. Other than maybe using a cache drive. Also, will using a Really fast drive (7200RPM or more) for the parity drive possibly improve this performance?
Rod