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Top Forums UNIX for Dummies Questions & Answers SAN and Disk I/O ... do we care? Post 302454945 by jim mcnamara on Monday 20th of September 2010 10:51:54 AM
Old 09-20-2010
Normally a logical volume (lun) is based on all of the disks in a given SAN device. You do not tell the SAN where to store a lun. Period.

The SAN software can be confiured for different types of RAID settings and SAN software does all sorts of tuning and caching. If what you saw is WAY out of line, ask your disk guy to monitor what is going on. He/she can make adjustments.

The "disk" stuff you see df -h or iostat in the OS is the logical presentation of a filesystem on the OS, never a single physical disk. Don't conflate logical volumes and physical disks, which is what you seem to be doing.
 

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BIOCTL(8)						    BSD System Manager's Manual 						 BIOCTL(8)

NAME
bioctl -- RAID management interface SYNOPSIS
bioctl device command [arg [...]] DESCRIPTION
RAID device drivers which support management functionality can register their services with the bio(4) driver. bioctl then can be used to manage the RAID controller's properties. COMMANDS
The following commands are supported: show [disks | volumes] Without any argument by default bioctl will show information about all volumes and the logical disks used on them. If disks is specified, only information about physical disks will be shown. If volumes is specified, only information about the volumes will be shown. alarm [disable | enable | silence | test] Control the RAID card's alarm functionality, if supported. By default if no argument is specified, its current state will be shown. Optionally the disable, enable, silence, or test arguments may be specified to enable, disable, silence, or test the RAID card's alarm. blink start channel:target.lun | stop channel:target.lun Instruct the device at channel:target.lun to start or cease blinking, if there's ses(4) support in the enclosure. hotspare add channel:target.lun | remove channel:target.lun Create or remove a hot-spare drive at location channel:target.lun. passthru add DISKID channel:target.lun | remove channel:target.lun Create or remove a pass-through device. The DISKID argument specifies the disk that will be used for the new device, and it will be created at the location channel:target.lun. NOTE: Removing a pass-through device that has a mounted filesys- tem will lead to undefined behaviour. check start VOLID | stop VOLID Start or stop consistency volume check in the volume with index VOLID. NOTE: Not many RAID controllers support this fea- ture. create volume VOLID DISKIDs [SIZE] STRIPE RAID_LEVEL channel:target.lun Create a volume at index VOLID. The DISKIDs argument will specify the first and last disk, i.e.: 0-3 will use the disks 0, 1, 2, and 3. The SIZE argument is optional and may be specified if not all available disk space is wanted (also dependent of the RAID_LEVEL). The volume will have a stripe size defined in the STRIPE argument and it will be located at channel:target.lun. remove volume VOLID channel:target.lun Remove a volume at index VOLID and located at channel:target.lun. NOTE: Removing a RAID volume that has a mounted filesystem will lead to undefined behaviour. EXAMPLES
The following command, executed from the command line, shows the status of the volumes and its logical disks on the RAID controller: $ bioctl arcmsr0 show Volume Status Size Device/Label RAID Level Stripe ================================================================= 0 Building 468G sd0 ARC-1210-VOL#00 RAID 6 128KB 0% done 0:0 Online 234G 0:0.0 noencl <WDC WD2500YS-01SHB1 20.06C06> 0:1 Online 234G 0:1.0 noencl <WDC WD2500YS-01SHB1 20.06C06> 0:2 Online 234G 0:2.0 noencl <WDC WD2500YS-01SHB1 20.06C06> 0:3 Online 234G 0:3.0 noencl <WDC WD2500YS-01SHB1 20.06C06> To create a RAID 5 volume on the SCSI 0:15.0 location on the disks 0, 1, 2, and 3, with stripe size of 64Kb on the first volume ID, using all available free space on the disks: $ bioctl arcmsr0 create volume 0 0-3 64 5 0:15.0 To remove the volume 0 previously created at the SCSI 0:15.0 location: $ bioctl arcmsr0 remove volume 0 0:15.0 SEE ALSO
arcmsr(4), bio(4), cac(4), ciss(4), mfi(4) HISTORY
The bioctl command first appeared in OpenBSD 3.8, it was rewritten for NetBSD 5.0. AUTHORS
The bioctl interface was written by Marco Peereboom <marco@openbsd.org> and was rewritten with multiple features by Juan Romero Pardines <xtraeme@NetBSD.org>. BSD
March 16, 2008 BSD
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