On Mon, 2002-04-08 at 16:16, Ryland Bingham wrote:
> Is this limit for LVM in Linux in General?
>
> >>There is a fdisk table limit is 4 primaries, one of which may
> >>be of extended type, and a total maximum of 13 to 16 depending
> >>on hard drive type (IDE v SCSI).
> >>
> >>-- Russ Herrold
>
> Using redhat 7.1 and 7.2, I've created as many as 37 partitions on a
> single drive. I think the theoretical limit is 64. I install mainframe
> OS's (z/OS z/VM VSE) in Linux using Flexes emulation. To achieve the
> best I/O performance on the emulated DASD I need many raw(no linux file
> system) partitions(up to 30 on a 80GB drive) to match the size of a real
> Mainframe Dasd devices.
>
> I'm very interested in LVM if it can be used to dynamically handle a
> large number of partitions. I've not found any practical guideline on
> implementation only white papers and the such. Any body got experience
> or references?
I RTFS and found in lvm.h:
/*
* absolute limits for VGs, PVs per VG and LVs per VG
*/
#define ABS_MAX_VG 99
#define ABS_MAX_PV 256
#define ABS_MAX_LV 256 /* caused by 8 bit minor */
where:
PV == physical volumes (i.e. block devices that can be used with LVM)
VG == volume groups (i.e. block devices from which you will carve out
LV's)
LV == logical volumes (i.e. block devices you format and mount)
I've personally got a box at home with like 12 or 15 or so of them, and
make a few more temporary LV's at times.
However, I'm not 100% sure you can do "real" RAW I/O to an LV. If by
"many raw partitions" you mean a block device to which you can do RAW
I/O, I don't know if LVM will work. Try a google search.
--
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#!/usr/bin/perl -w
$_='while(read+STDIN,$_,2048){$a=29;$b=73;$c=142;$t=255;@t=map
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[$_%8]}(16..271);if((@a=unx"C*",$_)[20]&48){$h=5;$_=unxb24,join
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print+x"C*",@a}';s/x/pack+/g;eval
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