storage

镜像和层 镜像是由一些只读并且描绘文件系统区别的层组成的.它们一层一层堆叠起来,组成了镜像的基础文件系统.这些层都是只读的. 下图是由4层构成的ubuntu镜像: 而docker存储驱动的职责就是将这些层堆叠起来.并提供一个统一的视图.让我们觉得跟普通文件系统没什么区别. 当你创建了一个容器时.会在镜像的层上再添加一层叫做"容器层(container layer)",所有在运行中的容器中所做的修改操作,都是影响的这一层. 看下图 内容可寻址的存储 docker 1.10 开始,介绍了一种全新的寻址镜像和层上数据的存储模型.之前的镜像和层上数据的存放,都是通过随机UUID存放.新模型采用一种安全的内容hash来存放. 新模型特点包括提高了安全性.防止了id冲突,保证了pull,push,load,save操作后的数据一致性.并且更好的提供了层之间的共享问题. 参考图片: 容器层还是random uuid 对于新的模型,原先旧模型的镜像数据需要重新计算id来迁移.这些操作会在你运行新版本docker进程后自动执行. 镜像较多的话会比较耗资源.如需手工迁移请参考官方文档. 容器和层 容器和镜像主要区别就在于容器多了最上层的容器层.所有在容器中的修改操作,都是影响的容器各自的容器层.底下镜像的层都是只读不变的. 下图展示了多个容器共享同一个镜像,但是拥有各自的容器层.互相不受影响.

Is it possible to read and write to a local sqlite file from a chrome packaged app? I currently already read and write to a json file with app data that is locally stored on the harddrive but I also want to be able to do this with a sqlite database. I need it to be local and not on drive since I will interact with it from other (non chrome) processes as well. And even loading the file from drive (using sync filesystem instead of filesystem), I have no clue how to go about accessing a sqlite file SQLite support for Chrome Packaged Apps would be great. After all, Chrome on the desktop and on

In SQL Server you can use FLOAT or REAL to store floating point values the storage format of which is cleared defined by the IEEE 754 standard. For fixed point values we can use DECIMAL type (which has a synonym NUMERIC ). However I'm not pretty sure how SQL Server store DECIMAL values internally. For example, if I define a table and insert a row like this: IF OBJECT_ID('dbo.test_number_types') IS NOT NULL DROP TABLE dbo.test_number_types; CREATE TABLE dbo.test_number_types ( id INT IDENTITY(1, 1), c1 NUMERIC(5, 4) ) GO INSERT INTO dbo.test_number_types(c1)VALUES(5.7456); When I use DBCC PAGE

My app is a background service without any GUI. Apk size is about 9 MB. When I installed this app on Samsung Note II(OS 4.4.2), application size is 18.55 MB, on Samsung Galaxy S4 37 MB and on Samsung Galaxy S5 69.47 MB. I already found a similar question but no solution at: Different installed app size on different devices Thanks for prompt response. It depends on which android os you are installing. After Kitkat they have introduced ART : ART (Android RunTime) is the next version of Dalvik. Dalvik is the runtime, bytecode, and VM used by the Android system for running Android applications.

After reading the Android documentation on storing files, I see that External Storage can include both a removable sd card AND storage that is internal to the device, i.e. not removable. Is there a way to distinguish between removable storage and non-removable storage when choosing to save a file to External Storage? I think you can't reliably distinguish between internal and external (SD) storage. At first glance it might seem like you can use something like Environment.isExternalStorageRemovable() but this isn't reliable, because your "primary external" storage device might very well be the

How Does HDFS store data? I want to store huge files in a compressed fashion. E.g : I have a 1.5 GB of file, with default replication factor of 3. It requires (1.5)*3 = 4.5 GB of space. I believe currently no implicit compression of data takes place. Is there a technique to compress the file and store it in HDFS to save disk space ? HDFS stores any file in a number of 'blocks'. The block size is configurable on a per file basis, but has a default value (like 64/128/256 MB) So given a file of 1.5 GB, and block size of 128 MB, hadoop would break up the file into ~12 blocks (12 x 128 MB ~= 1.5GB)