Character Devices vs. Block Devices
Hello, A quick ls of my dev directory revealed that each one of my hard drives is considered a character device by the system. Example: crw-r- 2 root operator 116, 0x00010002 Aug 19 16:09 /dev/ad0 crw-r- 2 root operator 116, 0 Aug 19 16:09 /dev/ad0a crw-r- 2 root operator 116, 1 Aug 19 16:09 /dev/ad0b crw-r- 2 root operator 116, 2 Aug 19 16:09 /dev/ad0c crw-r- 2 root operator 116, 3 Aug 19 16:09 /dev/ad0d crw-r- 2 root operator 116, 4 Aug 19 16:09 /dev/ad0e crw-r- 2 root operator 116, 5 Aug 19 16:09 /dev/ad0f crw-r- 2 root operator 116, 6 Aug 19 16:09 /dev/ad0g crw-r- 2 root operator 116, 7 Aug 19 16:09 /dev/ad0h What I am confused about, aren't hard drives treated as block devices on most systems? What am I missing? Regards, Weston To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Character Devices vs. Block Devices
From: Weston M. Price [EMAIL PROTECTED] Date: Tue, 1 Oct 2002 15:19:59 + Sender: [EMAIL PROTECTED] Hello, A quick ls of my dev directory revealed that each one of my hard drives is considered a character device by the system. Example: crw-r- 2 root operator 116, 0x00010002 Aug 19 16:09 /dev/ad0 crw-r- 2 root operator 116, 0 Aug 19 16:09 /dev/ad0a crw-r- 2 root operator 116, 1 Aug 19 16:09 /dev/ad0b crw-r- 2 root operator 116, 2 Aug 19 16:09 /dev/ad0c crw-r- 2 root operator 116, 3 Aug 19 16:09 /dev/ad0d crw-r- 2 root operator 116, 4 Aug 19 16:09 /dev/ad0e crw-r- 2 root operator 116, 5 Aug 19 16:09 /dev/ad0f crw-r- 2 root operator 116, 6 Aug 19 16:09 /dev/ad0g crw-r- 2 root operator 116, 7 Aug 19 16:09 /dev/ad0h What I am confused about, aren't hard drives treated as block devices on most systems? What am I missing? Nothing. I can't comment on most systems, but block devices were eliminated from FreeBSD in V4. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: [EMAIL PROTECTED] Phone: +1 510 486-8634 To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Character Devices vs. Block Devices
So, given this, I am assuming that hard drives are treated as raw devices exclusively? That is, no intermediate buffers are maintained between the user process and the device: From The Design and Implementation of the 4.4 BSD operating system: The character interface does not copy the user data into a kernel buffer before putting then on an I/O queue. Rather, it arranges to have the I/O done directly to or from the address space of the process. Is this valid on FreeBSD? Regard, Weston On Tuesday 01 October 2002 03:19 pm, Weston M. Price wrote: Hello, A quick ls of my dev directory revealed that each one of my hard drives is considered a character device by the system. Example: crw-r- 2 root operator 116, 0x00010002 Aug 19 16:09 /dev/ad0 crw-r- 2 root operator 116, 0 Aug 19 16:09 /dev/ad0a crw-r- 2 root operator 116, 1 Aug 19 16:09 /dev/ad0b crw-r- 2 root operator 116, 2 Aug 19 16:09 /dev/ad0c crw-r- 2 root operator 116, 3 Aug 19 16:09 /dev/ad0d crw-r- 2 root operator 116, 4 Aug 19 16:09 /dev/ad0e crw-r- 2 root operator 116, 5 Aug 19 16:09 /dev/ad0f crw-r- 2 root operator 116, 6 Aug 19 16:09 /dev/ad0g crw-r- 2 root operator 116, 7 Aug 19 16:09 /dev/ad0h What I am confused about, aren't hard drives treated as block devices on most systems? What am I missing? Regards, Weston To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Character Devices vs. Block Devices
On Tue, 1 Oct 2002, Weston M. Price wrote: So, given this, I am assuming that hard drives are treated as raw devices exclusively? That is, no intermediate buffers are maintained between the user process and the device: Nope, there is buffering for the file system interface. I dont remember the exact reasons for nuking the block devices, but I think it has to do with the new VM subsystem and the integrated buffer cache/VM, but my memory may be failing. If you want a more acurate answer, search the archives for -hackers and -current Is this valid on FreeBSD? Nope. The book was written before FreeBSD nuked block devices. Fer Regard, Weston On Tuesday 01 October 2002 03:19 pm, Weston M. Price wrote: Hello, A quick ls of my dev directory revealed that each one of my hard drives is considered a character device by the system. Example: crw-r- 2 root operator 116, 0x00010002 Aug 19 16:09 /dev/ad0 crw-r- 2 root operator 116, 0 Aug 19 16:09 /dev/ad0a crw-r- 2 root operator 116, 1 Aug 19 16:09 /dev/ad0b crw-r- 2 root operator 116, 2 Aug 19 16:09 /dev/ad0c crw-r- 2 root operator 116, 3 Aug 19 16:09 /dev/ad0d crw-r- 2 root operator 116, 4 Aug 19 16:09 /dev/ad0e crw-r- 2 root operator 116, 5 Aug 19 16:09 /dev/ad0f crw-r- 2 root operator 116, 6 Aug 19 16:09 /dev/ad0g crw-r- 2 root operator 116, 7 Aug 19 16:09 /dev/ad0h What I am confused about, aren't hard drives treated as block devices on most systems? What am I missing? Regards, Weston To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
