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vfs: update VFS help

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Nick Craig-Wood 2020-06-26 18:28:33 +01:00
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vfs/help.go
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@ -3,20 +3,39 @@ package vfs
// Help contains text describing file and directory caching to add to // Help contains text describing file and directory caching to add to
// the command help. // the command help.
var Help = ` var Help = `
### Directory Cache ### VFS - Virtual File System
Using the ` + "`--dir-cache-time`" + ` flag, you can set how long a This command uses the VFS layer. This adapts the cloud storage objects
that rclone uses into something which looks much more like a disk
filing system.
Cloud storage objects have lots of properties which aren't like disk
files - you can't extend them or write to the middle of them, so the
VFS layer has to deal with that. Because there is no one right way of
doing this there are various options explained below.
The VFS layer also implements a directory cache - this caches info
about files and directories (but not the data) in memory.
### VFS Directory Cache
Using the ` + "`--dir-cache-time`" + ` flag, you can control long a
directory should be considered up to date and not refreshed from the directory should be considered up to date and not refreshed from the
backend. Changes made locally in the mount may appear immediately or backend. Changes made through the mount will appear immediately or
invalidate the cache. However, changes done on the remote will only invalidate the cache.
be picked up once the cache expires if the backend configured does not
support polling for changes. If the backend supports polling, changes
will be picked up on within the polling interval.
Alternatively, you can send a ` + "`SIGHUP`" + ` signal to rclone for --dir-cache-time duration Time to cache directory entries for. (default 5m0s)
it to flush all directory caches, regardless of how old they are. --poll-interval duration Time to wait between polling for changes.
Assuming only one rclone instance is running, you can reset the cache
like this: However, changes made directoy on the cloud storage by the web
interface or a different copy of rclone will only be picked up once
the directory cache expires if the backend configured does not support
polling for changes. If the backend supports polling, changes will be
picked up on within the polling interval.
You can send a ` + "`SIGHUP`" + ` signal to rclone for it to flush all
directory caches, regardless of how old they are. Assuming only one
rclone instance is running, you can reset the cache like this:
kill -SIGHUP $(pidof rclone) kill -SIGHUP $(pidof rclone)
@ -29,40 +48,41 @@ Or individual files or directories:
rclone rc vfs/forget file=path/to/file dir=path/to/dir rclone rc vfs/forget file=path/to/file dir=path/to/dir
### File Buffering ### VFS File Buffering
The ` + "`--buffer-size`" + ` flag determines the amount of memory, The ` + "`--buffer-size`" + ` flag determines the amount of memory,
that will be used to buffer data in advance. that will be used to buffer data in advance.
Each open file descriptor will try to keep the specified amount of Each open file will try to keep the specified amount of data in memory
data in memory at all times. The buffered data is bound to one file at all times. The buffered data is bound to one open file and won't be
descriptor and won't be shared between multiple open file descriptors shared.
of the same file.
This flag is a upper limit for the used memory per open file. The
buffer will only use memory for data that is downloaded but not not
yet read. If the buffer is empty, only a small amount of memory will
be used.
This flag is a upper limit for the used memory per file descriptor.
The buffer will only use memory for data that is downloaded but not
not yet read. If the buffer is empty, only a small amount of memory
will be used.
The maximum memory used by rclone for buffering can be up to The maximum memory used by rclone for buffering can be up to
` + "`--buffer-size * open files`" + `. ` + "`--buffer-size * open files`" + `.
### File Caching ### VFS File Caching
These flags control the VFS file caching options. The VFS layer is These flags control the VFS file caching options. File caching is
used by rclone mount to make a cloud storage system work more like a necessary to make the VFS layer appear compatible with a normal file
normal file system. system. It can be disabled at the cost of some compatibility.
You'll need to enable VFS caching if you want, for example, to read For example you'll need to enable VFS caching if you want to read and
and write simultaneously to a file. See below for more details. write simultaneously to a file. See below for more details.
Note that the VFS cache works in addition to the cache backend and you Note that the VFS cache is separate from the cache backend and you may
may find that you need one or the other or both. find that you need one or the other or both.
--cache-dir string Directory rclone will use for caching. --cache-dir string Directory rclone will use for caching.
--vfs-cache-mode CacheMode Cache mode off|minimal|writes|full (default off)
--vfs-cache-max-age duration Max age of objects in the cache. (default 1h0m0s) --vfs-cache-max-age duration Max age of objects in the cache. (default 1h0m0s)
--vfs-cache-mode string Cache mode off|minimal|writes|full (default "off") --vfs-cache-max-size SizeSuffix Max total size of objects in the cache. (default off)
--vfs-cache-poll-interval duration Interval to poll the cache for stale objects. (default 1m0s) --vfs-cache-poll-interval duration Interval to poll the cache for stale objects. (default 1m0s)
--vfs-cache-max-size int Max total size of objects in the cache. (default off) --vfs-write-back duration Time to writeback files after last use when using cache. (default 5s)
If run with ` + "`-vv`" + ` rclone will print the location of the file cache. The If run with ` + "`-vv`" + ` rclone will print the location of the file cache. The
files are stored in the user cache file area which is OS dependent but files are stored in the user cache file area which is OS dependent but
@ -74,9 +94,10 @@ The higher the cache mode the more compatible rclone becomes at the
cost of using disk space. cost of using disk space.
Note that files are written back to the remote only when they are Note that files are written back to the remote only when they are
closed so if rclone is quit or dies with open files then these won't closed and if they haven't been accessed for --vfs-write-back
get written back to the remote. However they will still be in the on second. If rclone is quit or dies with files that haven't been
disk cache. uploaded, these will be uploaded next time rclone is run with the same
flags.
If using --vfs-cache-max-size note that the cache may exceed this size If using --vfs-cache-max-size note that the cache may exceed this size
for two reasons. Firstly because it is only checked every for two reasons. Firstly because it is only checked every
@ -119,32 +140,65 @@ first.
This mode should support all normal file system operations. This mode should support all normal file system operations.
If an upload fails it will be retried up to --low-level-retries times. If an upload fails it will be retried at exponentially increasing
intervals up to 1 minute.
#### --vfs-cache-mode full #### --vfs-cache-mode full
In this mode all reads and writes are buffered to and from disk. When In this mode all reads and writes are buffered to and from disk. When
a file is opened for read it will be downloaded in its entirety first. data is read from the remote this is buffered to disk as well.
This may be appropriate for your needs, or you may prefer to look at In this mode the files in the cache will be sparse files and rclone
the cache backend which does a much more sophisticated job of caching, will keep track of which bits of the files it has dowloaded.
including caching directory hierarchies and chunks of files.
In this mode, unlike the others, when a file is written to the disk, So if an application only reads the starts of each file, then rclone
it will be kept on the disk after it is written to the remote. It will only buffer the start of the file. These files will appear to be
will be purged on a schedule according to ` + "`--vfs-cache-max-age`" + `. their full size in the cache, but they will be sparse files with only
the data that has been downloaded present in them.
This mode should support all normal file system operations. This mode should support all normal file system operations and is
otherwise identical to --vfs-cache-mode writes.
If an upload or download fails it will be retried up to ### VFS Performance
--low-level-retries times.
### Case Sensitivity These flags may be used to enable/disable features of the VFS for
performance or other reasons.
In particular S3 and Swift benefit hugely from the --no-modtime flag
(or use --use-server-modtime for a slightly different effect) as each
read of the modification time takes a transaction.
--no-checksum Don't compare checksums on up/download.
--no-modtime Don't read/write the modification time (can speed things up).
--no-seek Don't allow seeking in files.
--read-only Mount read-only.
When rclone reads files from a remote it reads them in chunks. This
means that rather than requesting the whole file rclone reads the
chunk specified. This is advantageous because some cloud providers
account for reads being all the data requested, not all the data
delivered.
Rclone will keep doubling the chunk size requested starting at
--vfs-read-chunk-size with a maximum of --vfs-read-chunk-size-limit
unless it is set to "off" in which case there will be no limit.
--vfs-read-chunk-size SizeSuffix Read the source objects in chunks. (default 128M)
--vfs-read-chunk-size-limit SizeSuffix Max chunk doubling size (default "off")
Sometimes rclone is delivered reads or writes out of order. Rather
than seeking rclone will wait a short time for the in sequence read or
write to come in. These flags only come into effect when not using an
on disk cach file.
--vfs-read-wait duration Time to wait for in-sequence read before seeking. (default 20ms)
--vfs-write-wait duration Time to wait for in-sequence write before giving error. (default 1s)
### VFS Case Sensitivity
Linux file systems are case-sensitive: two files can differ only Linux file systems are case-sensitive: two files can differ only
by case, and the exact case must be used when opening a file. by case, and the exact case must be used when opening a file.
Windows is not like most other operating systems supported by rclone.
File systems in modern Windows are case-insensitive but case-preserving: File systems in modern Windows are case-insensitive but case-preserving:
although existing files can be opened using any case, the exact case used although existing files can be opened using any case, the exact case used
to create the file is preserved and available for programs to query. to create the file is preserved and available for programs to query.
@ -155,7 +209,7 @@ file systems case-sensitive but that is not the default
The "--vfs-case-insensitive" mount flag controls how rclone handles these The "--vfs-case-insensitive" mount flag controls how rclone handles these
two cases. If its value is "false", rclone passes file names to the mounted two cases. If its value is "false", rclone passes file names to the mounted
file system as is. If the flag is "true" (or appears without a value on file system as-is. If the flag is "true" (or appears without a value on
command line), rclone may perform a "fixup" as explained below. command line), rclone may perform a "fixup" as explained below.
The user may specify a file name to open/delete/rename/etc with a case The user may specify a file name to open/delete/rename/etc with a case