Romex Software Forum

Hey Everyone,

I'm playing around with a trial of PrimoCache Pro and I have a basic question regarding the defer-write mechanism.

I am hoping to utilize PrimoCache on a camera collection system. As images are taken at a set trigger interval they are written to the D: drive on the collection computer. We have some processing software which operates on new images once they are finished being written to disk. The goal is to maintain throughput by having the cameras writing to the cache while processing operates on disk written files. With writing directly to disk we can potential encounter I/O issues when using short trigger delays.

I was assuming that the image (ex. D:\Image001.iiq) wouldn't appear in Windows File Explorer until the defer-write interval has expired and the cache flushed, but this isn't the case. As soon as the image is taken the file appears and the processing software detects it. By monitoring the Total Write (Req) and Total Write (Disk) I can see that the defer-write is occurring at the specified interval.

So I guess my confusion is based on the file D:\Image001.iiq appearing and being detected immediately even though it hasn't been physically written to disk yet. With the warnings regarding potential loss of data with defer-write I figured the data wouldn't be accessible until the specified interval.

Can somebody please help me understand this above behavior?

Thanks,

-- Dan

There seems to be a misunderstanding about how Defer-Write operates. It works by initially writing data to the cache. At this point, PrimoCache immediately notifies Windows and applications that files have been written to "disk", allowing them to proceed. PrimoCache does the internal works, so these files can be accessed as if they were already on the physical disk.

When latency expires, PrimoCache commits files in the cache to the physical disk. The risk is that if a system crash or power outage occurs before this write-back process is completed, any data residing solely in the cache will be lost, potentially leading to file corruption.

Gotcha. Thanks for helping me understand how it works.