+
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
+S3QL, a locally
+mounted network backed file system with the features I need.
+
+
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.
+
+
It is simple to use. I'm using it on Debian Wheezy, where the
+package is included already. So to get started, run apt-get
+install s3ql. Next, pick a storage provider. I ended up picking
+Greenqloud, after reading their nice recipe on
+how
+to use S3QL with their Amazon S3 service, 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
+S3QL
+Filesystem for HPC Storage 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.
+
+
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 bucket-name below. In addition, one need
+the API login and password, and a locally created password. Store it
+all in ~root/.s3ql/authinfo2 like this:
+
+
+[s3c]
+storage-url: s3c://s.greenqloud.com:443/bucket-name
+backend-login: API-login
+backend-password: API-password
+fs-passphrase: local-password
+
+
+
I create my local passphrase using pwget 50 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:
+
+
+# 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.
+#
+
+
The next step is mounting the file system to make the storage available.
+
+
+# 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
+#
+
+
+
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:
+
+
+# umount.s3ql /s3ql
+#
+
+
+
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:
+
+
+# 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.
+#
+
+
+
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 dd. 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.
+
+
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:
+
+
+# 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.
+#
+
+
+
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:
+
+
+# s3qlctrl upload-meta /s3ql
+# s3qlctrl flushcache /s3ql
+#
+
+
+
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:
+
+
+# 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)
+#
+
+
+
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
+Greenqloud,
+Google Drive,
+Amazon S3 web serivces,
+Rackspace and
+Crowncloud. 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.
+
+
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
+"An
+Innovative Parallel Cloud Storage System using OpenStackâs SwiftObject
+Store and Transformative Parallel I/O Approach" by Hsing-Bung
+Chen, Benjamin McClelland, David Sherrill, Alfred Torrez, Parks Fields
+and Pamela Smith. Please have a look.
+
+
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
+my
+test code to check file system semantics, 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.
+
+
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
+Tarsnap service, 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.
+
+
As usual, if you use Bitcoin and want to show your support of my
+activities, please send Bitcoin donations to my address
+15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.
+
+