diff options
Diffstat (limited to 'Documentation/blockdev')
| -rw-r--r-- | Documentation/blockdev/README.DAC960 | 2 | ||||
| -rw-r--r-- | Documentation/blockdev/cciss.txt | 39 | ||||
| -rw-r--r-- | Documentation/blockdev/drbd/data-structure-v9.txt | 38 | ||||
| -rw-r--r-- | Documentation/blockdev/floppy.txt | 8 | ||||
| -rw-r--r-- | Documentation/blockdev/nbd.txt | 38 | ||||
| -rw-r--r-- | Documentation/blockdev/paride.txt | 2 | ||||
| -rw-r--r-- | Documentation/blockdev/ramdisk.txt | 29 | ||||
| -rw-r--r-- | Documentation/blockdev/zram.txt | 113 |
8 files changed, 211 insertions, 58 deletions
diff --git a/Documentation/blockdev/README.DAC960 b/Documentation/blockdev/README.DAC960 index 0e8f618ab53..bd85fb9dc6e 100644 --- a/Documentation/blockdev/README.DAC960 +++ b/Documentation/blockdev/README.DAC960 @@ -214,7 +214,7 @@ replacing "/usr/src" with wherever you keep your Linux kernel source tree: make config make bzImage (or zImage) -Then install "arch/i386/boot/bzImage" or "arch/i386/boot/zImage" as your +Then install "arch/x86/boot/bzImage" or "arch/x86/boot/zImage" as your standard kernel, run lilo if appropriate, and reboot. To create the necessary devices in /dev, the "make_rd" script included in diff --git a/Documentation/blockdev/cciss.txt b/Documentation/blockdev/cciss.txt index 89698e8df7d..b79d0a13e7c 100644 --- a/Documentation/blockdev/cciss.txt +++ b/Documentation/blockdev/cciss.txt @@ -78,6 +78,16 @@ The device naming scheme is: /dev/cciss/c1d1p2 Controller 1, disk 1, partition 2 /dev/cciss/c1d1p3 Controller 1, disk 1, partition 3 +CCISS simple mode support +------------------------- + +The "cciss_simple_mode=1" boot parameter may be used to prevent the driver +from putting the controller into "performant" mode. The difference is that +with simple mode, each command completion requires an interrupt, while with +"performant mode" (the default, and ordinarily better performing) it is +possible to have multiple command completions indicated by a single +interrupt. + SCSI tape drive and medium changer support ------------------------------------------ @@ -88,14 +98,12 @@ You must enable "SCSI tape drive support for Smart Array 5xxx" and "SCSI support" in your kernel configuration to be able to use SCSI tape drives with your Smart Array 5xxx controller. -Additionally, note that the driver will not engage the SCSI core at init -time. The driver must be directed to dynamically engage the SCSI core via -the /proc filesystem entry which the "block" side of the driver creates as -/proc/driver/cciss/cciss* at runtime. This is because at driver init time, -the SCSI core may not yet be initialized (because the driver is a block -driver) and attempting to register it with the SCSI core in such a case -would cause a hang. This is best done via an initialization script -(typically in /etc/init.d, but could vary depending on distribution). +Additionally, note that the driver will engage the SCSI core at init +time if any tape drives or medium changers are detected. The driver may +also be directed to dynamically engage the SCSI core via the /proc filesystem +entry which the "block" side of the driver creates as +/proc/driver/cciss/cciss* at runtime. This is best done via a script. + For example: for x in /proc/driver/cciss/cciss[0-9]* @@ -169,3 +177,18 @@ is issued which positions the tape to a known position. Typically you must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example) before i/o can proceed again to a tape drive which was reset. +There is a cciss_tape_cmds module parameter which can be used to make cciss +allocate more commands for use by tape drives. Ordinarily only a few commands +(6) are allocated for tape drives because tape drives are slow and +infrequently used and the primary purpose of Smart Array controllers is to +act as a RAID controller for disk drives, so the vast majority of commands +are allocated for disk devices. However, if you have more than a few tape +drives attached to a smart array, the default number of commands may not be +enought (for example, if you have 8 tape drives, you could only rewind 6 +at one time with the default number of commands.) The cciss_tape_cmds module +parameter allows more commands (up to 16 more) to be allocated for use by +tape drives. For example: + + insmod cciss.ko cciss_tape_cmds=16 + +Or, as a kernel boot parameter passed in via grub: cciss.cciss_tape_cmds=8 diff --git a/Documentation/blockdev/drbd/data-structure-v9.txt b/Documentation/blockdev/drbd/data-structure-v9.txt new file mode 100644 index 00000000000..1e52a0e3262 --- /dev/null +++ b/Documentation/blockdev/drbd/data-structure-v9.txt @@ -0,0 +1,38 @@ +This describes the in kernel data structure for DRBD-9. Starting with +Linux v3.14 we are reorganizing DRBD to use this data structure. + +Basic Data Structure +==================== + +A node has a number of DRBD resources. Each such resource has a number of +devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD +device is represented by a block device locally. + +The DRBD objects are interconnected to form a matrix as depicted below; a +drbd_peer_device object sits at each intersection between a drbd_device and a +drbd_connection: + + /--------------+---------------+.....+---------------\ + | resource | device | | device | + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + +--------------+---------------+.....+---------------+ + : : : : : + : : : : : + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + \--------------+---------------+.....+---------------/ + +In this table, horizontally, devices can be accessed from resources by their +volume number. Likewise, peer_devices can be accessed from connections by +their volume number. Objects in the vertical direction are connected by double +linked lists. There are back pointers from peer_devices to their connections a +devices, and from connections and devices to their resource. + +All resources are in the drbd_resources double-linked list. In addition, all +devices can be accessed by their minor device number via the drbd_devices idr. + +The drbd_resource, drbd_connection, and drbd_device objects are reference +counted. The peer_device objects only serve to establish the links between +devices and connections; their lifetime is determined by the lifetime of the +device and connection which they reference. diff --git a/Documentation/blockdev/floppy.txt b/Documentation/blockdev/floppy.txt index 6ccab88705c..e2240f5ab64 100644 --- a/Documentation/blockdev/floppy.txt +++ b/Documentation/blockdev/floppy.txt @@ -39,17 +39,17 @@ Module configuration options ============================ If you use the floppy driver as a module, use the following syntax: -modprobe floppy <options> +modprobe floppy floppy="<options>" Example: - modprobe floppy omnibook messages + modprobe floppy floppy="omnibook messages" If you need certain options enabled every time you load the floppy driver, you can put: - options floppy omnibook messages + options floppy floppy="omnibook messages" -in /etc/modprobe.conf. +in a configuration file in /etc/modprobe.d/. The floppy driver related options are: diff --git a/Documentation/blockdev/nbd.txt b/Documentation/blockdev/nbd.txt index aeb93ffe641..271e607304d 100644 --- a/Documentation/blockdev/nbd.txt +++ b/Documentation/blockdev/nbd.txt @@ -4,43 +4,13 @@ can use a remote server as one of its block devices. So every time the client computer wants to read, e.g., /dev/nb0, it sends a request over TCP to the server, which will reply with the data read. - This can be used for stations with low disk space (or even diskless - - if you boot from floppy) to borrow disk space from another computer. - Unlike NFS, it is possible to put any filesystem on it, etc. It should - even be possible to use NBD as a root filesystem (I've never tried), - but it requires a user-level program to be in the initrd to start. - It also allows you to run block-device in user land (making server - and client physically the same computer, communicating using loopback). - - Current state: It currently works. Network block device is stable. - I originally thought that it was impossible to swap over TCP. It - turned out not to be true - swapping over TCP now works and seems - to be deadlock-free, but it requires heavy patches into Linux's - network layer. - + This can be used for stations with low disk space (or even diskless) + to borrow disk space from another computer. + Unlike NFS, it is possible to put any filesystem on it, etc. + For more information, or to download the nbd-client and nbd-server tools, go to http://nbd.sf.net/. - Howto: To setup nbd, you can simply do the following: - - First, serve a device or file from a remote server: - - nbd-server <port-number> <device-or-file-to-serve-to-client> - - e.g., - root@server1 # nbd-server 1234 /dev/sdb1 - - (serves sdb1 partition on TCP port 1234) - - Then, on the local (client) system: - - nbd-client <server-name-or-IP> <server-port-number> /dev/nb[0-n] - - e.g., - root@client1 # nbd-client server1 1234 /dev/nb0 - - (creates the nb0 device on client1) - The nbd kernel module need only be installed on the client system, as the nbd-server is completely in userspace. In fact, the nbd-server has been successfully ported to other operating diff --git a/Documentation/blockdev/paride.txt b/Documentation/blockdev/paride.txt index e4312676bdd..ee6717e3771 100644 --- a/Documentation/blockdev/paride.txt +++ b/Documentation/blockdev/paride.txt @@ -412,6 +412,6 @@ have in your mail headers, when sending mail to the list server. You might also find some useful information on the linux-parport web pages (although they are not always up to date) at - http://www.torque.net/parport/ + http://web.archive.org/web/*/http://www.torque.net/parport/ diff --git a/Documentation/blockdev/ramdisk.txt b/Documentation/blockdev/ramdisk.txt index 6c820baa19a..fe2ef978d85 100644 --- a/Documentation/blockdev/ramdisk.txt +++ b/Documentation/blockdev/ramdisk.txt @@ -36,21 +36,30 @@ allowing one to squeeze more programs onto an average installation or rescue floppy disk. -2) Kernel Command Line Parameters +2) Parameters --------------------------------- +2a) Kernel Command Line Parameters + ramdisk_size=N ============== This parameter tells the RAM disk driver to set up RAM disks of N k size. The -default is 4096 (4 MB) (8192 (8 MB) on S390). +default is 4096 (4 MB). + +2b) Module parameters - ramdisk_blocksize=N - =================== + rd_nr + ===== + /dev/ramX devices created. -This parameter tells the RAM disk driver how many bytes to use per block. The -default is 1024 (BLOCK_SIZE). + max_part + ======== + Maximum partition number. + rd_size + ======= + See ramdisk_size. 3) Using "rdev -r" ------------------ @@ -64,9 +73,9 @@ the RAM disk dynamically grows as data is being written into it, a size field is not required. Bits 11 to 13 are not currently used and may as well be zero. These numbers are no magical secrets, as seen below: -./arch/i386/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF -./arch/i386/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000 -./arch/i386/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000 +./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF +./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000 +./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000 Consider a typical two floppy disk setup, where you will have the kernel on disk one, and have already put a RAM disk image onto disk #2. @@ -85,7 +94,7 @@ The command line equivalent is: "prompt_ramdisk=1" Putting that together gives 2^15 + 2^14 + 0 = 49152 for an rdev word. So to create disk one of the set, you would do: - /usr/src/linux# cat arch/i386/boot/zImage > /dev/fd0 + /usr/src/linux# cat arch/x86/boot/zImage > /dev/fd0 /usr/src/linux# rdev /dev/fd0 /dev/fd0 /usr/src/linux# rdev -r /dev/fd0 49152 diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt new file mode 100644 index 00000000000..0595c3f56cc --- /dev/null +++ b/Documentation/blockdev/zram.txt @@ -0,0 +1,113 @@ +zram: Compressed RAM based block devices +---------------------------------------- + +* Introduction + +The zram module creates RAM based block devices named /dev/zram<id> +(<id> = 0, 1, ...). Pages written to these disks are compressed and stored +in memory itself. These disks allow very fast I/O and compression provides +good amounts of memory savings. Some of the usecases include /tmp storage, +use as swap disks, various caches under /var and maybe many more :) + +Statistics for individual zram devices are exported through sysfs nodes at +/sys/block/zram<id>/ + +* Usage + +Following shows a typical sequence of steps for using zram. + +1) Load Module: + modprobe zram num_devices=4 + This creates 4 devices: /dev/zram{0,1,2,3} + (num_devices parameter is optional. Default: 1) + +2) Set max number of compression streams + Compression backend may use up to max_comp_streams compression streams, + thus allowing up to max_comp_streams concurrent compression operations. + By default, compression backend uses single compression stream. + + Examples: + #show max compression streams number + cat /sys/block/zram0/max_comp_streams + + #set max compression streams number to 3 + echo 3 > /sys/block/zram0/max_comp_streams + +Note: +In order to enable compression backend's multi stream support max_comp_streams +must be initially set to desired concurrency level before ZRAM device +initialisation. Once the device initialised as a single stream compression +backend (max_comp_streams equals to 1), you will see error if you try to change +the value of max_comp_streams because single stream compression backend +implemented as a special case by lock overhead issue and does not support +dynamic max_comp_streams. Only multi stream backend supports dynamic +max_comp_streams adjustment. + +3) Select compression algorithm + Using comp_algorithm device attribute one can see available and + currently selected (shown in square brackets) compression algortithms, + change selected compression algorithm (once the device is initialised + there is no way to change compression algorithm). + + Examples: + #show supported compression algorithms + cat /sys/block/zram0/comp_algorithm + lzo [lz4] + + #select lzo compression algorithm + echo lzo > /sys/block/zram0/comp_algorithm + +4) Set Disksize + Set disk size by writing the value to sysfs node 'disksize'. + The value can be either in bytes or you can use mem suffixes. + Examples: + # Initialize /dev/zram0 with 50MB disksize + echo $((50*1024*1024)) > /sys/block/zram0/disksize + + # Using mem suffixes + echo 256K > /sys/block/zram0/disksize + echo 512M > /sys/block/zram0/disksize + echo 1G > /sys/block/zram0/disksize + +Note: +There is little point creating a zram of greater than twice the size of memory +since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the +size of the disk when not in use so a huge zram is wasteful. + +5) Activate: + mkswap /dev/zram0 + swapon /dev/zram0 + + mkfs.ext4 /dev/zram1 + mount /dev/zram1 /tmp + +6) Stats: + Per-device statistics are exported as various nodes under + /sys/block/zram<id>/ + disksize + num_reads + num_writes + failed_reads + failed_writes + invalid_io + notify_free + zero_pages + orig_data_size + compr_data_size + mem_used_total + +7) Deactivate: + swapoff /dev/zram0 + umount /dev/zram1 + +8) Reset: + Write any positive value to 'reset' sysfs node + echo 1 > /sys/block/zram0/reset + echo 1 > /sys/block/zram1/reset + + This frees all the memory allocated for the given device and + resets the disksize to zero. You must set the disksize again + before reusing the device. + +Nitin Gupta +ngupta@vflare.org |