On 12.12.19 19:38, Damien Le Moal wrote: Hi, > zonefs is a very simple file system exposing each zone of a zoned block > device as a file. Unlike a regular file system with zoned block device > support (e.g. f2fs or the on-going btrfs effort), zonefs does not hide > the sequential write constraint of zoned block devices to the user. Just curious: what's the exact definition of "zoned" here ? Something like partitions ? Can these files then also serve as block devices for other filesystems ? Just a funny idea: could we handle partitions by a file system ? Even more funny idea: give file systems block device ops, so they can be directly used as such (w/o explicitly using loopdev) ;-) > Files representing sequential write zones of the device must be written > sequentially starting from the end of the file (append only writes). So, these files can only be accessed like a tape ? Assuming you're working ontop of standard block devices anyways (instead of tape-like media ;-)) - why introducing such a limitation ? > zonefs is not a POSIX compliant file system. It's goal is to simplify > the implementation of zoned block devices support in applications by > replacing raw block device file accesses with a richer file based API, > avoiding relying on direct block device file ioctls which may > be more obscure to developers. ioctls ? Last time I checked, block devices could be easily accessed via plain file ops (read, write, seek, ...). You can basically treat them just like big files of fixed size. > One example of this approach is the > implementation of LSM (log-structured merge) tree structures (such as > used in RocksDB and LevelDB) The same LevelDB as used eg. in Chrome browser, which destroys itself every time a little temporary problem (eg. disk full) occours ? If that's the usecase I'd rather use an simple in-memory table instead and and enough swap, as leveldb isn't reliable enough for persistent data anyways :p > on zoned block devices by allowing SSTables > to be stored in a zone file similarly to a regular file system rather > than as a range of sectors of a zoned device. The introduction of the > higher level construct "one file is one zone" can help reducing the > amount of changes needed in the application while at the same time > allowing the use of zoned block devices with various programming > languages other than C. Why not just simply use files on a suited filesystem (w/ low block io overhead) or LVM volumes ? --mtx -- Dringender Hinweis: aufgrund existenzieller Bedrohung durch "Emotet" sollten Sie *niemals* MS-Office-Dokumente via E-Mail annehmen/öffenen, selbst wenn diese von vermeintlich vertrauenswürdigen Absendern zu stammen scheinen. Andernfalls droht Totalschaden. --- Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu. --- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@xxxxxxxxx -- +49-151-27565287
