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10.5: How to create a RAM disk larger than 2.2GB
Authored by: mayathemacjedi on Mar 02, '09 08:30:28PM

I thought I was logged in when I made the original post, but I guess I wasnt!

This is an EXCELLENT point that MKURON made about concatenation as opposed to striping and I didn't even think about that! Since soft RAID comes with some overhead as ROB_G stated (although not much cpu overhead was seen in my initial tests, I want to take a closer look now though). Concatenating would just basically use the secondary ram drive as "overflow" so to speak, and not having that soft stripe would squeeze that much more performance out of the solution. The reason for striping them was not for an increase in speed like one would get had they been multiple striped disks since physically it is coming from the same source [RAM]. Data flows as fast as it could when read/written to/from RAM and RAID stripes would not offer a benefit as the bus is maxed out presumably anyway. (Maybe some underground driver exists that can stripe paired dimms on the dual independent fsb's: ;0)) This soft RAID was done so that an application would be able to use the one larger logical disk for its caches and whatnot, and access it as one single larger volume (although slower due to the striping overhead mentioned by ROB_G). I will look into concatenating instead as it would be a LOT better of an option, and I think it will work. Some of the tests I ran included hashing out MD5's of large iso's, uncompressing archives to the same disk they are stored on (after copying to ram ran the same test on the ram disks), duplicating files, etc. Thanks for that insight ROB_G and MKURON and others, I will try to implement these ideas and see how far the rabbit hole goes!!

mayathemacjedi



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10.5: How to create a RAM disk larger than 2.2GB
Authored by: mayathemacjedi on Mar 09, '09 01:55:35AM

The "concat" verb in place of "stripe" works, and it eliminates the soft raid bottlenecks. Thanks guys for the tips!



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