| ccd.4 (75670) | ccd.4 (76175) |
|---|---|
| 1.\" $NetBSD: ccd.4,v 1.5 1995/10/09 06:09:09 thorpej Exp $ 2.\" 3.\" Copyright (c) 1994 Jason Downs. 4.\" Copyright (c) 1994, 1995 Jason R. Thorpe. 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions --- 18 unchanged lines hidden (view full) --- 27.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 30.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" | 1.\" $NetBSD: ccd.4,v 1.5 1995/10/09 06:09:09 thorpej Exp $ 2.\" 3.\" Copyright (c) 1994 Jason Downs. 4.\" Copyright (c) 1994, 1995 Jason R. Thorpe. 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions --- 18 unchanged lines hidden (view full) --- 27.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 30.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" |
| 35.\" $FreeBSD: head/share/man/man4/ccd.4 75670 2001-04-18 15:54:10Z ru $ | 35.\" $FreeBSD: head/share/man/man4/ccd.4 76175 2001-05-01 09:15:30Z schweikh $ |
| 36.\" 37.Dd August 9, 1995 38.Dt CCD 4 39.Os NetBSD 40.Sh NAME 41.Nm ccd 42.Nd Concatenated Disk driver 43.Sh SYNOPSIS | 36.\" 37.Dd August 9, 1995 38.Dt CCD 4 39.Os NetBSD 40.Sh NAME 41.Nm ccd 42.Nd Concatenated Disk driver 43.Sh SYNOPSIS |
| 44.Cd "pseudo-device ccd 4" | 44.Cd "device ccd 4" |
| 45.Sh DESCRIPTION 46The 47.Nm 48driver provides the capability of combining one or more disks/partitions 49into one virtual disk. 50.Pp 51This document assumes that you're familiar with how to generate kernels, | 45.Sh DESCRIPTION 46The 47.Nm 48driver provides the capability of combining one or more disks/partitions 49into one virtual disk. 50.Pp 51This document assumes that you're familiar with how to generate kernels, |
| 52how to properly configure disks and pseudo-devices in a kernel | 52how to properly configure disks and devices in a kernel |
| 53configuration file, and how to partition disks. 54.Pp 55Note that the 56.Sq raw 57partitions of the disks 58.Pa should not 59be combined. The kernel will only allow component partitions of type 60FS_BSDFFS (type 61.Dq Bx 4.2 62as shown as 63.Xr disklabel 8 ) . 64.Pp 65In order to compile in support for the ccd, you must add a line similar 66to the following to your kernel configuration file: 67.Bd -unfilled -offset indent | 53configuration file, and how to partition disks. 54.Pp 55Note that the 56.Sq raw 57partitions of the disks 58.Pa should not 59be combined. The kernel will only allow component partitions of type 60FS_BSDFFS (type 61.Dq Bx 4.2 62as shown as 63.Xr disklabel 8 ) . 64.Pp 65In order to compile in support for the ccd, you must add a line similar 66to the following to your kernel configuration file: 67.Bd -unfilled -offset indent |
| 68pseudo-device ccd 4 # concatenated disk devices | 68device ccd 4 # concatenated disk devices |
| 69.Ed 70.Pp 71The count argument is how many 72.Nm Ns 's 73memory is allocated for a boot time. In this example, no more than 4 74.Nm Ns s 75may be configured. As of the 76.Fx 3.0 77release, you do not need to 78configure your kernel with ccd but may instead use it as a kernel loadable 79module. Simply running | 69.Ed 70.Pp 71The count argument is how many 72.Nm Ns 's 73memory is allocated for a boot time. In this example, no more than 4 74.Nm Ns s 75may be configured. As of the 76.Fx 3.0 77release, you do not need to 78configure your kernel with ccd but may instead use it as a kernel loadable 79module. Simply running |
| 80.Nm ccdconfig | 80.Nm ccdconfig |
| 81will load the module into the kernel. 82.Pp 83A 84.Nm 85may be either serially concatenated or interleaved. To serially 86concatenate the partitions, specify the interleave factor of 0. 87Note that mirroring may not be used with an interleave factor of 0. 88.Pp --- 13 unchanged lines hidden (view full) --- 102is typically the size of a track, while for large reads, it is about a 103quarter of a track. 104(Note that this changes greatly depending on the 105number and speed of disks.) For instance, with eight 7,200 RPM drives 106on two Fast-Wide SCSI buses, this translates to about 128 for writes 107and 32 for reads. A larger interleave tends to work better when the 108disk is taking a multitasking load by localizing the file I/O from 109any given process onto a single disk. You lose sequential performance when | 81will load the module into the kernel. 82.Pp 83A 84.Nm 85may be either serially concatenated or interleaved. To serially 86concatenate the partitions, specify the interleave factor of 0. 87Note that mirroring may not be used with an interleave factor of 0. 88.Pp --- 13 unchanged lines hidden (view full) --- 102is typically the size of a track, while for large reads, it is about a 103quarter of a track. 104(Note that this changes greatly depending on the 105number and speed of disks.) For instance, with eight 7,200 RPM drives 106on two Fast-Wide SCSI buses, this translates to about 128 for writes 107and 32 for reads. A larger interleave tends to work better when the 108disk is taking a multitasking load by localizing the file I/O from 109any given process onto a single disk. You lose sequential performance when |
| 110you do this, but sequential performance is not usually an issue with a | 110you do this, but sequential performance is not usually an issue with a |
| 111multitasking load. 112.Pp 113An interleave factor must be specified when using a mirroring configuration, 114even when you have only two disks (i.e. the layout winds up being the same 115no matter what the interleave factor). The interleave factor will determine 116how I/O is broken up, however, and a value 128 or greater is recommended. 117.Pp 118CCD has an option for a parity disk, but does not currently implement it. --- 48 unchanged lines hidden (view full) --- 167If just one (or more) of the disks in a 168.Nm 169fails, the entire 170file system will be lost unless you are mirroring the disks. 171.Pp 172If one of the disks in a mirror is lost, you should still 173be able to backup your data. If a write error occurs, however, data 174read from that sector may be non-deterministic. It may return the data | 111multitasking load. 112.Pp 113An interleave factor must be specified when using a mirroring configuration, 114even when you have only two disks (i.e. the layout winds up being the same 115no matter what the interleave factor). The interleave factor will determine 116how I/O is broken up, however, and a value 128 or greater is recommended. 117.Pp 118CCD has an option for a parity disk, but does not currently implement it. --- 48 unchanged lines hidden (view full) --- 167If just one (or more) of the disks in a 168.Nm 169fails, the entire 170file system will be lost unless you are mirroring the disks. 171.Pp 172If one of the disks in a mirror is lost, you should still 173be able to backup your data. If a write error occurs, however, data 174read from that sector may be non-deterministic. It may return the data |
| 175prior to the write or it may return the data that was written. When a | 175prior to the write or it may return the data that was written. When a |
| 176write error occurs, you should recover and regenerate the data as soon 177as possible. 178.Pp | 176write error occurs, you should recover and regenerate the data as soon 177as possible. 178.Pp |
| 179Changing the interleave or other parameters for a | 179Changing the interleave or other parameters for a |
| 180.Nm 181disk usually destroys whatever data previously existed on that disk. 182.Sh FILES 183/dev/{,r}ccd* - ccd device special files. 184.Pp 185.Sh HISTORY 186The concatenated disk driver was originally written at the University of 187Utah. 188.Sh SEE ALSO 189.Xr dd 1 , 190.Xr ccdconfig 8 , 191.Xr config 8 , 192.Xr disklabel 8 , 193.Xr fsck 8 , 194.Xr MAKEDEV 8 , 195.Xr mount 8 , 196.Xr newfs 8 , 197.Xr vinum 8 | 180.Nm 181disk usually destroys whatever data previously existed on that disk. 182.Sh FILES 183/dev/{,r}ccd* - ccd device special files. 184.Pp 185.Sh HISTORY 186The concatenated disk driver was originally written at the University of 187Utah. 188.Sh SEE ALSO 189.Xr dd 1 , 190.Xr ccdconfig 8 , 191.Xr config 8 , 192.Xr disklabel 8 , 193.Xr fsck 8 , 194.Xr MAKEDEV 8 , 195.Xr mount 8 , 196.Xr newfs 8 , 197.Xr vinum 8 |