If an object are split into multiple fragments and fragments may not be adjacent to each other, there's are at least 2 I/O ATS uses when serving range requests:
+ One to read meta data about the object (for example: the fragment tables) + One for fetching requested data If we can get rid of fragment tables by: + Define a fixed fragment size for each cache span (or volume, stripe) + Have adaptive routing policies to route objects to appropriate spans (based on their sizes) Then we only need 1 I/O to serve range requests, right? On Mon, Jun 5, 2017 at 9:57 PM, Alan Carroll < solidwallofc...@yahoo-inc.com.invalid> wrote: > In practice the fragments are not all the same size. The sizing logic is a > bit sloppy because it was not considered important at the time to get the > fragments consistently sized (why does it matter if all fragments will be > read on a cache hit?). When I put in the range acceleration I didn't want > to deal with that change as well. With the POC update the fragment table is > still needed, even though the fragments for an object are consistent sized, > to hold state information about the fragments. > > > On Sunday, June 4, 2017, 11:24:52 PM CDT, Anh Le Duc (2) < > anh...@vng.com.vn> wrote: > > > @Alan: I saw your answer for my issue #2023 > <https://github.com/apache/trafficserver/issues/2023>. To handle range > requests, we must efficiently know which fragments to read. By using > fragment tables, we can achieve that purpose. > > For example: if we serve a range request of bytes 1000-2000, with fragment > tables, we know the Nth fragment (from the current one) containing > requested data. By continuously applying hash functions on the request's > key N times, we may effectively locate the fragment. > > My question is: if we split a specific object into multiple fragments > having the same size, are fragment tables useless? Because we can quickly > have: > > 1000/fragmentSize <= N = 2000 / fragmentSize > > > -- *Anh Le (Mr.)* *Senior Software Engineer* *Zalo Technical Dept., Zalo Group, **VNG Corporation* 5th floor, D29 Building, Pham Van Bach Street, Hanoi, Vietnam *M:* (+84) 987 816 461 *E:* anh...@vng.com.vn *W: *www.vng.com.vn <http://www.google.com/url?q=http%3A%2F%2Fwww.vng.com.vn&sa=D&sntz=1&usg=AFQjCNHYo7I_1mPESzfIvCNjLtAJOq8xsg> *“Make the Internet change Vietnamese lives”*
