Hi, the PDC system disk is not on the storage, just a 150GB partition for 
databases.
That's why I can't see how Windows did not let me in even on vmware console.
The requirements to have several DCs is a very nice trick from Microsoft to get 
more licenses...
There is no zfs command running on my .bashrc but, now you opened my eyes :
Just before entering the system via ssh, I tried to check the storage via our 
web interface,
and it was correctly responding, until I went to the Pool management, where the 
web interface
issued a "zpool list", and it showed me the available pools.
Then I opened the tree to see the filesystem..........and there it stopped 
responding.......
At least I understand why I could not enter the system anymore (not even on 
console...).
Last questions:
- shouldn't I find some logs into the svc/logs of the iscsi services? (I 
don't...)
- should I rise the swap space? (it's now 4.5GB, phys memory is 8GB).
- what may be the reasons of the pool failing? a zpool status shows it's all 
fine.
- any other way I can prevent this from happening?
Thanx so much!
Gabriele.
----------------------------------------------------------------------------------
Da: Jim Klimov
A: [email protected]
Cc: Gabriele Bulfon
Aldo Fornoni
Data: 9 novembre 2012 19.04.09 CET
Oggetto: Re: [discuss] illumos based ZFS storage failure
On 2012-11-09 18:01, Gabriele Bulfon wrote:
The Windows PDC for CIFS resides inside a VMWare5 machine.
This PDC, has also a disk mounted via a VMWare-iScsi resource on the
storage itself.
...
There is a kind of loop in this situation, but I suspect that all the
problem started with the iScsi not responding from the storage:
- the PDC did not let me in because it was angry with the missing disk
from VMWare-iScsci. If this is the case, is it normal that a Windows
server give me no way to enter when a disk is not responding?? Or should
I just think that the PDC was freezing by itself (but in this case, I
shouldn't see iscsi time out on vmware).
Do I understand correctly that the PDC VM itself is not hosted
on this storage (i.e. the OS disk is not iSCSIed from illumos)?
Just to clarify...
If the OS disk hung (due to iSCSI), it might cause the Windows
VM to hang, like any other OS. Inaccessibility due to a non-OS
drive does seem strange... it should have been kicked off after
a timeout, I think.
- the CIFS was not responding because the PDC was timing out
That's why there should be several DCs ;)
I don't understand why the storage was not giving me the bash, though!
And, I could not find any trace of errors, logs or whatsoever about
iscsi problems.
Sometimes I had hit conditions where ZFS/ZPOOL commands began
hanging and never exiting, and holding a shell. Ultimately this
was solved by either a reboot, or (rarely) by ZFS completing its
internal housekeeping (like those deferred deletions).
If your .bashrc does something like "zfs list" or "df -k", as
I like doing on my systems to get a quick overview upon login,
this can cause the never-appearance of a shell.
Also the hanging processes can pile up and exhaust address space
or even the process table, and the OS is inaccessible due to
either no memory ("can't fork", if it is able to write that)
or to constant context swapping in-kernel to switch between
myriads of processes. For me, Solaris has survived about 10x
as many sleeping processes as Linux in similar setups, but
nothing is infinitely sturdy.
Finally, the address space could also be exhausted by something
big in /tmp or /var/run or other "swap"-based filesystems (if
your tmpfs is virtual-memory-backed, and no limit is artificially
imposed by the mount options on /tmp). This by itself might be
the cause - precluding programs from working and maybe hanging
the iSCSI server (at least, the userspace program parts).
Whatever the reason, it is likely that the storage server could
not write into its log files during the problem (i.e. syslog died)
hence no reports to be found.
HTH,
//Jim Klimov



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