Difference between revisions of "Operating Systems 2014F Lecture 14"
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Make filesystems do, on modern filesystem, rather than trying to optimize the storage of small files. It's not so much filesize that is the issue. | Make filesystems do, on modern filesystem, rather than trying to optimize the storage of small files. It's not so much filesize that is the issue. | ||
Floppy disks vs. hard disks | |||
What is fast and what is slow? | |||
fast - reading what is under the drive head at any given time. As long as you keep the head there, you can read the entire concentric circle really fast. That's the fastest operation you are going to get? | |||
What's slow? Moving the head from one part of the disk to another - that's a slow operation. | |||
Intuitively, why is it that slow? you have to move it with extreme precision.. | |||
moving data hard - seek time - the time it takes to move the drive head from one area to another on the disk. | |||
coordinate system goes by Cylinder Head Sector | |||
How many heads there are, which of these, and which cylinder, and which sector, which is a count around. | |||
Revision as of 10:33, 5 November 2014
How does an operating system know it's accessed memory it doesn't have access to? A lot of you said segments.
Filesystems - normally operating system mechanisms are
talking about access to hardware systems, persistent storage. - abstraction for persistent storage. Storage that maintains it's state when it loses power. A couple of challenges with persistent storage. What's weird about storing things in persistent storage? It's slow. durability and persistent.
Going to make errors - we should be able to recover from them. Maybe not fix everything, but preserve most of the data. This is a huge burden on filesystems. Filesystem development tends to be very slow in practice. Whatever code you have doing this, has to do this right. Older filesystems tend to be more trustworthy, when hardware changes, bugs you didn't know where in the filesystem may come up.
what do we have today? Indexed filesystems.
There is typically a minimum storage allocation given to every file. That's the minimum size of a file, it's taking up 4 k / 8 k. this is not strictly true for all file systems. There was a filesystem that allowed arbitrarily sized files. (ReiserFS)
Unifying a keyvalue store for smaller and larger filesystems wasn't considered a priority.
Make filesystems do, on modern filesystem, rather than trying to optimize the storage of small files. It's not so much filesize that is the issue.
Floppy disks vs. hard disks
What is fast and what is slow?
fast - reading what is under the drive head at any given time. As long as you keep the head there, you can read the entire concentric circle really fast. That's the fastest operation you are going to get?
What's slow? Moving the head from one part of the disk to another - that's a slow operation.
Intuitively, why is it that slow? you have to move it with extreme precision..
moving data hard - seek time - the time it takes to move the drive head from one area to another on the disk.
coordinate system goes by Cylinder Head Sector
How many heads there are, which of these, and which cylinder, and which sector, which is a count around.