topic Re: Brocade fencing with GFS2 and root on SAN in Operating System - Linux

Brocade fencing with GFS2 and root on SAN

B Cave — Sun, 29 Jun 2008 21:47:24 GMT

hi,

I have an EVA4400 with a few servers. each server has a private dedicated vdisk assigned to it. This is formatted for its / fs (ext3). /boot and swap is on local disk. Each server also has 2nd and 3rd vdisks presented to them.

I am considering using brocade fencing (have a brocade switch), but am concerned that brocade fencing for the shared storage will also block my "/" filesystem - should i just stick to gnbd?

Re: Brocade fencing with GFS2 and root on SAN

Ivan Ferreira — Sun, 29 Jun 2008 23:19:01 GMT

>>> This is formatted for its / fs (ext3). /boot and swap is on local disk.

Ok, your / is on local disks.

>>> but am concerned that brocade fencing for the shared storage will also block my "/" filesystem

Why do you think that if you / is on local disks? Besides, if a node is fenced, there is a reason for that, in fact, is better if you have a power switch or a ILO fencing also to reboot the node.

Re: Brocade fencing with GFS2 and root on SAN

B Cave — Sun, 29 Jun 2008 23:35:36 GMT

each server has a private dedicated vdisk presented to it - this is formatted for its root filesystem - so / is on SAN.

/boot - /dev/cciss/c0d0p1 (local)
swap - /dev/cciss/c0d0p2 (local
/ - /dev/sda1 (SAN,unshared, ext3)
/gfs/storage - /dev/sdb1 (SAN, shared, GFS)

Now if 1 node gets fenced, it is done by san - so server would basically crash?
The data on GFS is a cache for a custom application - has data that can easily be regenerated. if it is fenced, how would it go about recovering?

Re: Brocade fencing with GFS2 and root on SAN

Ivan Ferreira — Sun, 29 Jun 2008 23:41:55 GMT

Ok, now I understand.

Normally is good idea to have / on local disks also. But in this case, yes, fencing will block access to your root file system and your server will crash.

>> if it is fenced, how would it go about recovering?

First, you must know the cause of the fencing. Once you are sure that the problem was solved, you must manually enable the sanswitch port with portenable.

Re: Brocade fencing with GFS2 and root on SAN

B Cave — Mon, 30 Jun 2008 00:14:46 GMT

ok, great thanks.

busy looking for info on how ilo fencing works.