Thursday, July 4, 2013

Google paper on optimal provisioning of flash

Here is a nice article on the different types of memory in a computer. The top of the pyramid like L1/L2 cache is close to the CPU and is fast, but is costlier and small in terms of storage. The bottom of the pyramid is far to the CPU and is slow, but is cheaper and large in terms of storage.

The mentioned article doesn't talk about SSD. SSDs are fast and consume less power when compared to HDD. This is one of the reason why Laptops with SSD are ligher and faster. But, SSD are costlier in terms of per GB cost when compared to a similar capacity HDD.
Some of the recent computers have a hybrid of SSD and HDD to gain the benefits of both. Data is flushed from/into flash based on the LRU or the FIFO algorithms. This makes computers work faster without spending heavily on a SSD only computer. This is refered to as Express Cache and more about it here.

Google has published a paper called Janus applying the same above concepts to a data center level. Though SSD is fast, it's cost makes it prohibitive to have SSD only data center. So, the data is moved between the SSD and HDD based on the LRU and FIFO algorithms. Thanks to the GigaOm article for pointing to Janus.

One interesting aspect is the below observation in the paper

Our results show that the recommendations allow 28% of read operations to be served from flash by placing 1% of our data on flash.

As mentioned in the earlier blog Google had been driving the Big Data space by publishing papers and the Janus papers is one of them.

Another area how Google had been spurring innovation has been by killing the Google Reader. This has lead to lot of other alternative online rss aggregators. I had been trying feedly and theoldreader, and finally settled using theoldreader. Google Reader and theoldreader are pretty close and it feels at home using the oldreader.

Although, Google had been spurring the innovation in many areas, it had also been killing innovation. With Google Reader active others were scared of Google to start an alternative rss aggregator or infact any other product similar to what Google had been offering.

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