Bill Davidsen wrote:
Mike Wright wrote:
Bill Davidsen wrote:
Mike Wright wrote:
I came up with a solution that uses LVM and it works a *charm*,
albeit, probably because of large block sizes relative to the 16M
size of the ramdisks, seems inefficient (costs 25% each). Maybe I
can tune these and get better.
pvcreate /dev/ram15
pvcreate /dev/ram14
pvcreate /dev/ram13
pvcreate /dev/ram12
vgcreate my36Mdisk /dev/ram15 /dev/ram14 /dev/ram13
vgcreate my12Mdisk /dev/ram/12
lvcreate -n myRamDisk1 -L 36M my36Mdisk
lvcreate -n myRamDisk2 -L 12M my12Mdisk
Wow that sounds complex, why not just make the ramdisks larger? Just
use the boot parameter which sets that:
ramdisk_size=N
where N is the size in kilobytes, so for 256M you specify 262144.
Thanks for that advice.
I ended up making the ramdisks smaller which gave me greater
granularity. Then when the volume groups were created I specified 64K
extents instead of the default 16M. That gave two benefits: there was
almost no wasted space in the VG, and the data that I copied over used
less than half of the space of the original.
In thinking about this related to another issue, I remember that you can
also just create a single arbitrary ramdisk and mount it:
mount -t tmpfs -o size=270m tmpfs /mnt/tmp
which gives you a 270MB ramdisk on /mnt/tmp. No choice of filesystem
type, always tmpfs, but for what I wanted adequate.
I'm doing some testing on performance tips, and am using this for testing.
That accomplishes everything I wanted when combined with "mount --move"
and lets me get rid of a horrendous script :D
create temporary work area.
copy work area to temporary work area.
mount --move to original work area.
Work work work until done
mount --move original work area back to temporary area.
copy temporary work area to original work area.
unmount temporary work area.
If it hits swap I can live with that.
Awesome, Bill!
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