11-13-2007
First off: if you tar something, the command will read something on your disk (a bunch of files) and then create an archive from it, writing that to the disk (most of times). What else then seeing activity on your disk do you suppose will happen?
Additionally i would like to clarify what the "% tm_act" field in the output of iostat means:
The OS has a sensor, regularily asking the disk if it is busy or not. When the disks aswers half of the times "I'm busy", then the "% tm_act" will be 50%. If the disk answers every time "I'm busy" then tm_act will be 100%, etc.. A disk answers with "busy", when there are requested operations not yet fulfilled, read or write. If many very small requests go to the disk the chance of the sensor asking exactly when one such operation is still open goes up - much more so than the real activity of the disk.
So, "100% busy" does not necessarily mean the disk is at the edge of its trasnfer bandwidth. It could mean either that because the disk is getting relatively few but big requests (example: stream I/O) but it could also mean that the disk is getting a lot of requests which are relatively small so that the disk is occupied most of the time, but not using its complete transfer bandwith.
To find out which is the case analyse the corresponding "Kb_read" and "Kb_wrtn" column from iostat. You know how much a modern disk drive can approximately handle (~17MB/second) physically and bypassing any cache. Compare your data to this (rule-of-thumb-)value and you will get a more detailed picture.
bakunin
Last edited by bakunin; 11-13-2007 at 08:42 AM..
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LEARN ABOUT HPUX
fsvoladm
fsvoladm(1M) fsvoladm(1M)
NAME
fsvoladm - VxFS volume administration utility
SYNOPSIS
[bias]
DESCRIPTION
The utility performs administrative tasks, such as adding, removing, resizing, and encapsulating volumes in a specified VERITAS File Sys-
tem. mount_point specifies the directory on which the file system is mounted.
volname specifies the volume within the volume set.
By default, size, bias, and newsize are specified in units of disk blocks bytes). However, you can append or to the number to indicate
that the value is in kilobytes, megabytes, gigabytes, or terabytes, respectively.
Keywords
Adds a volume to a file system. The new space is available for allocation.
Removes an encapsulated volume from a file system
and restores the original contents of the volume. This operation can fail if there were significant changes to a file's allocations
on disk since encapsulation. A volume encapsulated with a bias cannot be deencapsulated.
Adds a volume to a file system,
making the contents of that volume, starting from offset bias, available as a file instead of free space.
The size of the encapsulated file is size - bias. bias must be smaller than size, and be a multiple of the file system block size.
The default value of bias is 0.
Displays the volumes in a file system.
Removes a volume from a file system.
Resizes one of the volumes in a file system.
In some circumstances, the command cannot resize a 100% full file system due to lack of space for updating structural information.
Check VxFS file systems on a regular basis; increase their size if they approach 100% capacity. This problem can also occur if the
file system is very busy. Free up space or reduce activity on the file system and try the resize again.
EXAMPLES
The following command adds the volume that is 10 gigabytes in size, to the file system
The following command removes the volume from the file system
The following command resizes the volume in the file system from its current size to 20 GB:
The following command displays the volumes in the file system
The following command encapsulates the volume The volume is ten gigabytes in size, resides in the file system and has the file name
The following command de-encapsulates the volume that was encapsulated in the previous example:
SEE ALSO
df_vxfs(1M), fsapadm(1M), fsvoladm(1M), mount_vxfs(1M), vxvset(1M),
fsvoladm(1M)