- <div class="entry">
- <div class="title"><a href="http://people.skolelinux.org/pere/blog/S3QL__a_locally_mounted_cloud_file_system___nice_free_software.html">S3QL, a locally mounted cloud file system - nice free software</a></div>
- <div class="date"> 9th April 2014</div>
- <div class="body"><p>For a while now, I have been looking for a sensible offsite backup
-solution for use at home. My requirements are simple, it must be
-cheap and locally encrypted (in other words, I keep the encryption
-keys, the storage provider do not have access to my private files).
-One idea me and my friends had many years ago, before the cloud
-storage providers showed up, was to use Google mail as storage,
-writing a Linux block device storing blocks as emails in the mail
-service provided by Google, and thus get heaps of free space. On top
-of this one can add encryption, RAID and volume management to have
-lots of (fairly slow, I admit that) cheap and encrypted storage. But
-I never found time to implement such system. But the last few weeks I
-have looked at a system called
-<a href="https://bitbucket.org/nikratio/s3ql/">S3QL</a>, a locally
-mounted network backed file system with the features I need.</p>
-
-<p>S3QL is a fuse file system with a local cache and cloud storage,
-handling several different storage providers, any with Amazon S3,
-Google Drive or OpenStack API. There are heaps of such storage
-providers. S3QL can also use a local directory as storage, which
-combined with sshfs allow for file storage on any ssh server. S3QL
-include support for encryption, compression, de-duplication, snapshots
-and immutable file systems, allowing me to mount the remote storage as
-a local mount point, look at and use the files as if they were local,
-while the content is stored in the cloud as well. This allow me to
-have a backup that should survive fire. The file system can not be
-shared between several machines at the same time, as only one can
-mount it at the time, but any machine with the encryption key and
-access to the storage service can mount it if it is unmounted.</p>
-
-<p>It is simple to use. I'm using it on Debian Wheezy, where the
-package is included already. So to get started, run <tt>apt-get
-install s3ql</tt>. Next, pick a storage provider. I ended up picking
-Greenqloud, after reading their nice recipe on
-<a href="https://greenqloud.zendesk.com/entries/44611757-How-To-Use-S3QL-to-mount-a-StorageQloud-bucket-on-Debian-Wheezy">how
-to use S3QL with their Amazon S3 service</a>, because I trust the laws
-in Iceland more than those in USA when it come to keeping my personal
-data safe and private, and thus would rather spend money on a company
-in Iceland. Another nice recipe is available from the article
-<a href="http://www.admin-magazine.com/HPC/Articles/HPC-Cloud-Storage">S3QL
-Filesystem for HPC Storage</a> by Jeff Layton in the HPC section of
-Admin magazine. When the provider is picked, figure out how to get
-the API key needed to connect to the storage API. With Greencloud,
-the key did not show up until I had added payment details to my
-account.</p>
-
-<p>Armed with the API access details, it is time to create the file
-system. First, create a new bucket in the cloud. This bucket is the
-file system storage area. I picked a bucket name reflecting the
-machine that was going to store data there, but any name will do.
-I'll refer to it as <tt>bucket-name</tt> below. In addition, one need
-the API login and password, and a locally created password. Store it
-all in ~root/.s3ql/authinfo2 like this:
-
-<p><blockquote><pre>
-[s3c]
-storage-url: s3c://s.greenqloud.com:443/bucket-name
-backend-login: API-login
-backend-password: API-password
-fs-passphrase: local-password
-</pre></blockquote></p>
-
-<p>I create my local passphrase using <tt>pwget 50</tt> or similar,
-but any sensible way to create a fairly random password should do it.
-Armed with these details, it is now time to run mkfs, entering the API
-details and password to create it:</p>
-
-<p><blockquote><pre>
-# mkdir -m 700 /var/lib/s3ql-cache
-# mkfs.s3ql --cachedir /var/lib/s3ql-cache --authfile /root/.s3ql/authinfo2 \
- --ssl s3c://s.greenqloud.com:443/bucket-name
-Enter backend login:
-Enter backend password:
-Before using S3QL, make sure to read the user's guide, especially
-the 'Important Rules to Avoid Loosing Data' section.
-Enter encryption password:
-Confirm encryption password:
-Generating random encryption key...
-Creating metadata tables...
-Dumping metadata...
-..objects..
-..blocks..
-..inodes..
-..inode_blocks..
-..symlink_targets..
-..names..
-..contents..
-..ext_attributes..
-Compressing and uploading metadata...
-Wrote 0.00 MB of compressed metadata.
-# </pre></blockquote></p>
-
-<p>The next step is mounting the file system to make the storage available.
-
-<p><blockquote><pre>
-# mount.s3ql --cachedir /var/lib/s3ql-cache --authfile /root/.s3ql/authinfo2 \
- --ssl --allow-root s3c://s.greenqloud.com:443/bucket-name /s3ql
-Using 4 upload threads.
-Downloading and decompressing metadata...
-Reading metadata...
-..objects..
-..blocks..
-..inodes..
-..inode_blocks..
-..symlink_targets..
-..names..
-..contents..
-..ext_attributes..
-Mounting filesystem...
-# df -h /s3ql
-Filesystem Size Used Avail Use% Mounted on
-s3c://s.greenqloud.com:443/bucket-name 1.0T 0 1.0T 0% /s3ql
-#
-</pre></blockquote></p>
-
-<p>The file system is now ready for use. I use rsync to store my
-backups in it, and as the metadata used by rsync is downloaded at
-mount time, no network traffic (and storage cost) is triggered by
-running rsync. To unmount, one should not use the normal umount
-command, as this will not flush the cache to the cloud storage, but
-instead running the umount.s3ql command like this:
-
-<p><blockquote><pre>
-# umount.s3ql /s3ql
-#
-</pre></blockquote></p>
-
-<p>There is a fsck command available to check the file system and
-correct any problems detected. This can be used if the local server
-crashes while the file system is mounted, to reset the "already
-mounted" flag. This is what it look like when processing a working
-file system:</p>
-
-<p><blockquote><pre>
-# fsck.s3ql --force --ssl s3c://s.greenqloud.com:443/bucket-name
-Using cached metadata.
-File system seems clean, checking anyway.
-Checking DB integrity...
-Creating temporary extra indices...
-Checking lost+found...
-Checking cached objects...
-Checking names (refcounts)...
-Checking contents (names)...
-Checking contents (inodes)...
-Checking contents (parent inodes)...
-Checking objects (reference counts)...
-Checking objects (backend)...
-..processed 5000 objects so far..
-..processed 10000 objects so far..
-..processed 15000 objects so far..
-Checking objects (sizes)...
-Checking blocks (referenced objects)...
-Checking blocks (refcounts)...
-Checking inode-block mapping (blocks)...
-Checking inode-block mapping (inodes)...
-Checking inodes (refcounts)...
-Checking inodes (sizes)...
-Checking extended attributes (names)...
-Checking extended attributes (inodes)...
-Checking symlinks (inodes)...
-Checking directory reachability...
-Checking unix conventions...
-Checking referential integrity...
-Dropping temporary indices...
-Backing up old metadata...
-Dumping metadata...
-..objects..
-..blocks..
-..inodes..
-..inode_blocks..
-..symlink_targets..
-..names..
-..contents..
-..ext_attributes..
-Compressing and uploading metadata...
-Wrote 0.89 MB of compressed metadata.
-#
-</pre></blockquote></p>
-
-<p>Thanks to the cache, working on files that fit in the cache is very
-quick, about the same speed as local file access. Uploading large
-amount of data is to me limited by the bandwidth out of and into my
-house. Uploading 685 MiB with a 100 MiB cache gave me 305 kiB/s,
-which is very close to my upload speed, and downloading the same
-Debian installation ISO gave me 610 kiB/s, close to my download speed.
-Both were measured using <tt>dd</tt>. So for me, the bottleneck is my
-network, not the file system code. I do not know what a good cache
-size would be, but suspect that the cache should e larger than your
-working set.</p>
-
-<p>I mentioned that only one machine can mount the file system at the
-time. If another machine try, it is told that the file system is
-busy:</p>
-
-<p><blockquote><pre>
-# mount.s3ql --cachedir /var/lib/s3ql-cache --authfile /root/.s3ql/authinfo2 \
- --ssl --allow-root s3c://s.greenqloud.com:443/bucket-name /s3ql
-Using 8 upload threads.
-Backend reports that fs is still mounted elsewhere, aborting.
-#
-</pre></blockquote></p>
-
-<p>The file content is uploaded when the cache is full, while the
-metadata is uploaded once every 24 hour by default. To ensure the
-file system content is flushed to the cloud, one can either umount the
-file system, or ask S3QL to flush the cache and metadata using
-s3qlctrl:
-
-<p><blockquote><pre>
-# s3qlctrl upload-meta /s3ql
-# s3qlctrl flushcache /s3ql
-#
-</pre></blockquote></p>
-
-<p>If you are curious about how much space your data uses in the
-cloud, and how much compression and deduplication cut down on the
-storage usage, you can use s3qlstat on the mounted file system to get
-a report:</p>
-
-<p><blockquote><pre>
-# s3qlstat /s3ql
-Directory entries: 9141
-Inodes: 9143
-Data blocks: 8851
-Total data size: 22049.38 MB
-After de-duplication: 21955.46 MB (99.57% of total)
-After compression: 21877.28 MB (99.22% of total, 99.64% of de-duplicated)
-Database size: 2.39 MB (uncompressed)
-(some values do not take into account not-yet-uploaded dirty blocks in cache)
-#
-</pre></blockquote></p>
-
-<p>I mentioned earlier that there are several possible suppliers of
-storage. I did not try to locate them all, but am aware of at least
-<a href="https://www.greenqloud.com/">Greenqloud</a>,
-<a href="http://drive.google.com/">Google Drive</a>,
-<a href="http://aws.amazon.com/s3/">Amazon S3 web serivces</a>,
-<a href="http://www.rackspace.com/">Rackspace</a> and
-<a href="http://crowncloud.net/">Crowncloud</A>. The latter even
-accept payment in Bitcoin. Pick one that suit your need. Some of
-them provide several GiB of free storage, but the prize models are
-quite different and you will have to figure out what suits you
-best.</p>
-
-<p>While researching this blog post, I had a look at research papers
-and posters discussing the S3QL file system. There are several, which
-told me that the file system is getting a critical check by the
-science community and increased my confidence in using it. One nice
-poster is titled
-"<a href="http://www.lanl.gov/orgs/adtsc/publications/science_highlights_2013/docs/pg68_69.pdf">An
-Innovative Parallel Cloud Storage System using OpenStack’s SwiftObject
-Store and Transformative Parallel I/O Approach</a>" by Hsing-Bung
-Chen, Benjamin McClelland, David Sherrill, Alfred Torrez, Parks Fields
-and Pamela Smith. Please have a look.</p>
-
-<p>Given my problems with different file systems earlier, I decided to
-check out the mounted S3QL file system to see if it would be usable as
-a home directory (in other word, that it provided POSIX semantics when
-it come to locking and umask handling etc). Running
-<a href="http://people.skolelinux.org/pere/blog/Testing_if_a_file_system_can_be_used_for_home_directories___.html">my
-test code to check file system semantics</a>, I was happy to discover that
-no error was found. So the file system can be used for home
-directories, if one chooses to do so.</p>
-
-<p>If you do not want a locally file system, and want something that
-work without the Linux fuse file system, I would like to mention the
-<a href="http://www.tarsnap.com/">Tarsnap service</a>, which also
-provide locally encrypted backup using a command line client. It have
-a nicer access control system, where one can split out read and write
-access, allowing some systems to write to the backup and others to
-only read from it.</p>
-
-<p>As usual, if you use Bitcoin and want to show your support of my
-activities, please send Bitcoin donations to my address
-<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&label=PetterReinholdtsenBlog">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
-</div>
- <div class="tags">
-
-
- Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/personvern">personvern</a>, <a href="http://people.skolelinux.org/pere/blog/tags/sikkerhet">sikkerhet</a>.
-
-
- </div>
- </div>
- <div class="padding"></div>
-