drbd for ramdisk

[witalij]

lab:~# drbdadm create-md mirror
open(/dev/ram0) failed: Invalid argument

<snip>
[pid 9884] 13:30:23.673121 munmap(0xb7fb5000, 4096) = 0
[pid 9884] 13:30:23.673265 open("/dev/ram0",
O_RDWR|O_DIRECT|O_LARGEFILE) = -1 EINVAL (Invalid argument)
[pid 9884] 13:30:23.673451 write(2, "open(/dev/ram0) failed: Invalid
"..., 41open(/dev/ram0) failed: Invalid argument
) = 41
[pid 9884] 13:30:23.673636 exit_group(20) = ?
Process 9884 detached
13:30:23.679505 <... rt_sigaction resumed> {SIG_DFL}, 8) = 0
13:30:23.683436 alarm(600) = 0
<snip>
dd if=/dev/zero of=/dev/shm/50MBdisk.bin bs=512 count=100K
losetup /dev/loop0 /dev/shm/50MBdisk.bin
drbdadm create-md mirror
drbdsetup /dev/drbd0 primary -o
mkfs.ext3 /dev/drbd0
mount /dev/drbd0 /mnt/

...

what is about the performance on loop device ? is not so fast,
it sees like i need one partition table on this device and one partition
like /dev/ram0p1
but i have problem to create it

[witalij]

Hi all !

how can i use DRBD with /dev/ram0

i try

dd if=/dev/zero of=/dev/ram0 bs=512 count=1024K
mkfs.xfs /dev/ram0

then

lab:~# drbdadm create-md mirror
open(/dev/ram0) failed: Invalid argument
Command 'drbdmeta /dev/drbd0 v08 /dev/ram0 internal create-md'
terminated with exit code 20
drbdadm aborting



this is my config

resource mirror {

protocol C;

on lab {
device /dev/drbd0;
disk /dev/ram0;
address 192.168.80.254:7788;
meta-disk internal;
}
on lector {
device /dev/drbd0;
disk /dev/ram0;
address 12.168.70.198:7788;
meta-disk internal;
}
disk {
on-io-error detach;
}

net {
max-buffers 2048;
ko-count 4;
}
syncer {
rate 10M;
al-extents 257;
}
startup {
wfc-timeout 0;
degr-wfc-timeout 120;
}
}


thanks

[Lars Ellenberg]

Post by witalij
Hi all !
how can i use DRBD with /dev/ram0
i try
dd if=/dev/zero of=/dev/ram0 bs=512 count=1024K
mkfs.xfs /dev/ram0
then
lab:~# drbdadm create-md mirror
open(/dev/ram0) failed: Invalid argument
Command 'drbdmeta /dev/drbd0 v08 /dev/ram0 internal create-md'
terminated with exit code 20
drbdadm aborting

latest drbd 8.2 git can work on ramdisk again.

what is your intended usage scenario,
what data do you want to store on a ramdisk?

[Leroy van Logchem]

Post by witalij
what is about the performance on loop device ? is not so fast,

Depends on the application. Loop devices are fast enough to fill
your memory within a few seconds.

[witalij]

Post by Leroy van Logchem

Post by witalij
what is about the performance on loop device ? is not so fast,

Depends on the application. Loop devices are fast enough to fill
your memory within a few seconds.

i have created ramdisk 32Gb on one server and export this over pvfs2
and 1Gbit to pgsql server it works well, and performance is ok
but i want mirror ramdisk to second server via drbd,
is loop debice fast enough ?