[linux-lvm] lvchange read ahead sectors

Karl Podesta kpodesta at redbrick.dcu.ie
Mon Feb 26 11:33:50 UTC 2007

Hi there, 

Does anyone know if I can change "read ahead sectors" to 1024 with LVM1 ?

I'm using lvm-1.0.5-129 on SUSE/SLES 8 - I have a logical volume with 
"read ahead sectors" set to 1024, and another one with the value as
0 (i.e. disabled). When I try to set the latter one to 1024 using 
"lvchange -r 1024", I get:

lvchange -- ERROR "Invalid argument" read ahead sector change

... and then in the lvchange man page I notice: 
 -r, --readahead ReadAheadSectors
              Change read ahead sector count per logical  between
              2 and 120.

If I can only set the value to 120, how come I have a volume with 1024? 
Is there a conversion needed between the two values? 

If anyone could shed some light on this or point me in the right 
direction, that would be great! Haven't had any joy looking through 
stuff on the net, or on the archives of this list... 

Many thanks!


PS - I realise this list is hosted on redhat.com, so sorry for any 
cross-distro pollination! :-)

Karl Podesta

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