[tahoe-dev] [tahoe-lafs] #962: Performance problems testing on a 45 disk Dual core 3.3Ghz 4G memory Box

tahoe-lafs trac at allmydata.org
Fri Feb 26 05:52:35 UTC 2010


#962: Performance problems testing on a 45 disk Dual core 3.3Ghz 4G memory Box
--------------------------------+-------------------------------------------
 Reporter:  stott               |           Owner:  somebody 
     Type:  defect              |          Status:  new      
 Priority:  major               |       Milestone:  undecided
Component:  website             |         Version:  1.5.0    
 Keywords:  performance memory  |   Launchpad_bug:           
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Comment(by zooko):

 Hm... It might be worth adding to [source:docs/performance.txt] a note
 about the fact that when downloading a mutable file you first have to wait
 for the entire file data to transfer from the storage servers to the
 gateway, and then the data streams from the gateway to your client. By
 "streams" here, I mean that your client can receive the first part of the
 data before the gateway has sent the last part of the data. Observe that
 the data of a mutable file does ''not'' "stream" from the storage servers
 all the way to your client—your client won't see the first part of the
 mutable file until after the gateway has received the ''last'' part of the
 mutable file from the storage servers.

 By contrast, if you download an immutable file it ''will'' "stream" all
 the way from the storage servers to your client—your client can see the
 first part of the immutable file as soon as the gateway receives the first
 block of each share from the storage servers, long before the gateway has
 seen the last part of the immutable file.

 This is potentially another reason to prefer immutable files over mutable
 files for performance when you're using Tahoe-LAFS v1.6. (How big of a
 performance issue this is depends on the details of your network and
 servers and the size of the file.)

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/962#comment:14>
tahoe-lafs <http://allmydata.org>
secure decentralized file storage grid


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