Oren Eini

aka Ayende Rahien

Oren Eini

CEO of RavenDB

a NoSQL Open Source Document Database

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oren@ravendb.net

+972 52-548-6969

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Comparison page for RavenDB and MongoDB

Sep 23 2005

SuperFetch & USB DisksOnKeys

time to read 2 min | 244 words

One of the things that bugged me about the SuperFetch demo in the PDC was the declaration that SuperFetch will try to utilize any USB memory on the system to augment the file cache.

On the face of it, it didn’t make sense; the access times for USB 2.0 and modern HD are about the same, with the balance tipping toward HD as the faster.

This post clears things up (look at the comments), apparently this is true for sequential reading, but not for random access, while flash memory excel in random access.

Even with the cost of encrypting it, there should be a good saving in performance that way. I’ll assume that the file cache will look like this:

Load to memory the most frequently used programs.
When you run out of the space reserved for the cache on RAM, target the USB drives on the system.
When you run out of USB drives, target the page file.

One consideration is what happens when you’ve external HD via USB? I’m pretty sure that they covered this option, though.

Cool technology, all around.

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FUTURE POSTS

Partial writes, IO_Uring and safety - one day from now
Configuration values & Escape hatches - 4 days from now
What happens when a sparse file allocation fails? - 6 days from now
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RECENT COMMENTS

Dmitry, Yes, but this is _known_ to be a 64 bits system - since we are allocating 3GB (not possible in 64 bits). Note t...

By Oren Eini on Answer: What does this code do?
That's why it is a good idea to compare the return value of `write` to the buffer size. "size_t" can be 32-bit on some system...

By Dmitry on Answer: What does this code do?
There's a reason we miss `write_exact` and `read_exact` from the standard library. In fact, I am surprised the chunk is actua...

By Pyth0n on Challenge: What does this code do?
kpvleeuwen, I agree, unfortunately I don't have anyone to ask off the top of my head. Thanks, I fixed the headers.

By Oren Eini on Performance discovery: IOPS vs. IOPS
It could be interesting to reach out to storage firmware developers and ask what write patterns they think would be useful ex...

By kpvleeuwen on Performance discovery: IOPS vs. IOPS

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