Changes between Version 102 and Version 103 of FAQ


Ignore:
Timestamp:
2014-03-05T02:42:54Z (11 years ago)
Author:
daira
Comment:

source:git/ -> source:

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  • FAQ

    v102 v103  
    55'''[=#Q1_why_tahoe_lafs Q1:] What is special about Tahoe-LAFS? Why should anyone care about it instead of [wiki:RelatedProjects#OtherProjects other distributed storage systems]?'''
    66
    7 A1: Tahoe-LAFS is the first Free !Software/Open Source storage technology to offer ''provider-independent security''.  ''Provider-independent security'' means that the integrity and confidentiality of your files is guaranteed by mathematics computed on the client side, and is independent of the servers, which may be owned and operated by someone else.  To learn more, read [source:git/docs/about.rst our one-page explanation].
     7A1: Tahoe-LAFS is the first Free !Software/Open Source storage technology to offer ''provider-independent security''.  ''Provider-independent security'' means that the integrity and confidentiality of your files is guaranteed by mathematics computed on the client side, and is independent of the servers, which may be owned and operated by someone else.  To learn more, read [source:docs/about.rst our one-page explanation].
    88
    99A2: Tahoe-LAFS provides reliable, fault-tolerant storage. Even if you do not need its security properties, you might want to use Tahoe-LAFS for extremely reliable storage. (Tahoe-LAFS's security features do a good job of staying out of your way when you don't need them.)
    … …  
    3333'''[=#Q4_where_are_the_docs Q4:] Where should I look for current documentation about the Tahoe-LAFS protocols?'''
    3434
    35 A: [source:git/docs/architecture.rst https://tahoe-lafs.org/trac/tahoe-lafs/browser/docs/architecture.rst]
     35A: [source:docs/architecture.rst https://tahoe-lafs.org/trac/tahoe-lafs/browser/docs/architecture.rst]
    3636
    3737'''[=#Q5_embedded_devices Q5:] Does Tahoe-LAFS work on embedded devices such as a [http://www.pogoplug.com PogoPlug] or an [http://openwrt.org OpenWRT] router?'''
    … …  
    4343'''[=#Q6_windows Q6:] Does Tahoe-LAFS work on Windows?'''
    4444
    45 A: Yes.  Follow [source:git/docs/quickstart.rst the standard quickstart instructions] to get Tahoe-LAFS running on Windows. (There was also an "Allmydata Windows client", but that is not actively maintained at the moment, and relied on some components that are not open-source.)
     45A: Yes.  Follow [source:docs/quickstart.rst the standard quickstart instructions] to get Tahoe-LAFS running on Windows. (There was also an "Allmydata Windows client", but that is not actively maintained at the moment, and relied on some components that are not open-source.)
    4646
    4747'''[=#Q7_mac_os_x Q7:] Does Tahoe-LAFS work on Mac OS X?'''
    4848
    49 A: Yes.  Follow [source:git/docs/quickstart.rst the standard quickstart instructions] on Mac OS X and it will result in a working command-line tool on Mac OS X just as it does on other Unixes.
     49A: Yes.  Follow [source:docs/quickstart.rst the standard quickstart instructions] on Mac OS X and it will result in a working command-line tool on Mac OS X just as it does on other Unixes.
    5050
    5151'''[=#Q8_storage_in_multiple_dirs Q8:] Can there be more than one storage directory on a storage node? So if a storage server contains 3 drives without RAID, can it use all 3 for storage?'''
    … …  
    118118'''[=#Q15.1_dedupe_dangers Q15.1:] Isn't deduplication dangerous? Can someone figure out whether or not I have a certain file?'''
    119119
    120 A: It is dangerous, even more so than most people realize! But, Tahoe-LAFS provides a defense: [source:git/docs/convergence-secret.rst].
     120A: It is dangerous, even more so than most people realize! But, Tahoe-LAFS provides a defense: [source:docs/convergence-secret.rst].
    121121
    122122'''[=#Q16_move_node_to_different_machine Q16:] If I move the client node base directory to different machine and start the client there, will the node have the same node ID as on the previous machine?'''
    … …  
    134134A: Tahoe-LAFS is designed to be unobtrusive. First of all, it doesn't start at all except when you tell it to—you start it with {{{tahoe start}}} and stop it with {{{tahoe stop}}}. Secondly, the software doesn't act as a server unless you configure it to do so—it isn't like peer-to-peer software which automatically acts as a server as well as a client. Thirdly, the client doesn't do anything except in response to the user starting an upload or a download—it doesn't do anything automatically or in the background (this might change in future, to support background repair for example, but probably only if you explicitly enable it). Fourthly, with two minor exceptions described below, the server doesn't do anything either, except in response to clients doing uploads or downloads. Finally, even when the server is actively serving clients it isn't too intensive of a process. It uses between 40 and 56 MB of RAM on a 64-bit Linux server. We used to run eight of them on a single-core 2 GHz Opteron and had plenty of CPU to spare, so it isn't too CPU intensive.
    135135
    136 The two minor exceptions are that the server periodically inspects all of the ciphertext that it is storing on behalf of clients. It is configured to do this "in the background", by doing it only for a second at a time and waiting for a few seconds in between each step. The intent is that this will not noticably impact other users of the same server. For all the details about when these background processes run and what they do, read the documentation in XXX [source:git/src/allmydata/storage/crawler.py?annotate=blame&rev=3cb99364e6a83d0064d2838a0c470278903e19ac storage/crawler.py] and [source:git/src/allmydata/storage/expirer.py?annotate=blame&rev=e76092e16c64019857441e9020d6d8ba2bdaa0bc storage/expirer.py].
     136The two minor exceptions are that the server periodically inspects all of the ciphertext that it is storing on behalf of clients. It is configured to do this "in the background", by doing it only for a second at a time and waiting for a few seconds in between each step. The intent is that this will not noticably impact other users of the same server. For all the details about when these background processes run and what they do, read the documentation in XXX [source:src/allmydata/storage/crawler.py?annotate=blame&rev=3cb99364e6a83d0064d2838a0c470278903e19ac storage/crawler.py] and [source:src/allmydata/storage/expirer.py?annotate=blame&rev=e76092e16c64019857441e9020d6d8ba2bdaa0bc storage/expirer.py].
    137137
    138138
    … …  
    157157
    158158A:
    159 Literal caps (or LIT caps) are simply the base32 encoding of the file data, and are used for very small files. The threshold is 55 bytes (source: XXX [source:git/src/allmydata/immutable/upload.py?annotate=blame&rev=196bd583b6c4959c60d3f73cdcefc9edda6a38ae#L1504 immutable/upload.py]), which is
     159Literal caps (or LIT caps) are simply the base32 encoding of the file data, and are used for very small files. The threshold is 55 bytes (source: XXX [source:src/allmydata/immutable/upload.py?annotate=blame&rev=196bd583b6c4959c60d3f73cdcefc9edda6a38ae#L1504 immutable/upload.py]), which is
    160160the break-even point at which the LIT filecap is the same length as a typical CHK filecap. They are sufficient (you don't even need network access to turn the LIT filecap into the data), and necessary (if you don't know the filecap for my data, you can't figure out the data). See this mailing list thread:
    161161* [//pipermail/tahoe-dev/2010-April/004235.html Storing a small file leads to a weird read capability] (especially [//pipermail/tahoe-dev/2010-April/004237.html this message by Brian Warner])
    … …  
    166166
    167167A:
    168 Yes. Tahoe-LAFS comes with an [source:git/docs/frontends/FTP-and-SFTP.rst SFTP server]. If you point [http://fuse.sourceforge.net/sshfs.html sshfs] at the SFTP server then you have access to Tahoe-LAFS through FUSE. Alternately, [wiki:pyFilesystem pyfilesystem] interfaces directly with Tahoe-LAFS through the latter's [source:git/docs/frontends/webapi.rst WAPI] and provides both FUSE and Microsoft Windows filesystem access. See #1353 for discussion of possible improvements to FUSE integration.
     168Yes. Tahoe-LAFS comes with an [source:docs/frontends/FTP-and-SFTP.rst SFTP server]. If you point [http://fuse.sourceforge.net/sshfs.html sshfs] at the SFTP server then you have access to Tahoe-LAFS through FUSE. Alternately, [wiki:pyFilesystem pyfilesystem] interfaces directly with Tahoe-LAFS through the latter's [source:docs/frontends/webapi.rst web-API] and provides both FUSE and Microsoft Windows filesystem access. See #1353 for discussion of possible improvements to FUSE integration.
    169169
    170170There could be performance problems with the FUSE interface if the apps that are using the filesystem use it in a way that doesn't fit Tahoe-LAFS's semantics, and the FUSE layer is required to make many copies of entire files in order to emulate the desired semantics. See [http://lists.alioth.debian.org/pipermail/freedombox-discuss/2011-November/003162.html Zooko's post to freedombox-discuss] and [https://plus.google.com/108313527900507320366/posts/ZrgdgLhV3NG Zooko's post to Google+].