Networker

Re: [Networker] DDS woes

2003-01-21 06:14:21
Subject: Re: [Networker] DDS woes
From: Davina Treiber <treiber AT HOTPOP DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 21 Jan 2003 06:14:29 -0500
On Tue, 21 Jan 2003 11:31:24 +0100, Andre Beck <networker AT IBH DOT DE> wrote:

>I'm lab-testing dynamic drive sharing with 6.2 in a SAN environment
>consisting of Compaq (aka HP) DL380s with Compaq (aka Emulex) FC HBAs,
>a Compaq (aka Brocade) FC switch, a MSA1000 RAID array (not of the most
>relevance here) and an Overland Neo loaderXpress with FCO card. There
>are some issues with DDS that disturb me:
>
>1) Whenever the shared tape is switched between the two servers (one
>   beeing the Networker server, the other beeing a storage node) Win2k
>   issues nonsense messages of illegal device removal (dunno exactly
>   how this would be called in an original W2k, got a localized german
>   version here) - it warns me that I would have illegally removed the
>   SDLT320 Tape Drive (note, not the medium, but the *drive*). It even
>   does this in the midst of a running backup. It's the same message
>   you get when you remove a PC-Card without shutting it down first.
>   According to the Legato docs I have installed the library drivers
>   on both W2ks and disabled the library, leaving all other levels of
>   removable media handling enabled. I've also tried with the entire
>   removable media service disabled, but the messages were still popping
>   up on both servers.
>   I've got the feeling that this whole issue is due to the FC HBAs
>   beeing plugged into hotplug PCI slots and thus beeing under removable
>   device control which is extended to all subdevices connected via them,
>   but I'm not sure whether this should make any difference.
>   The FC-2-SCSI Router on the FCO card is configured to hide its own
>   LUN.

Both of your postings this morning have intrigued me, for the reason that
you seem to be struggling with 6.2. My question is why? 6.2 is a
non-mainstream release of NetWorker designed to address two specific needs:
Unix style filenames in NDMP, and XP support. If you don't need either of
these then stick with the 6.1.x tree, it is better supported. I have heard
several reports of buggy behaviour in 6.2 and it is best avoided IMHO. The
problem is that is the highest release number so many users assume it is the
greatest and latest. However the same happened with 5.7 which was released
to provide early W2K support until 6.x was released, and that release was
short-lived too.

Your issue seems odd. My first reaction would be to blame RSM, but you say
you have disabled it. In any case, I would leave the whole service switched
off unless you have some other unrelated need for it. Second culprit would
be a possible lack of persistent binding. Devices can move about in W2K, and
persistent binding goes some way to sorting this out. There are 2 "buts"
here though. Firstly, Compaq have crippled the Emulex HBA when they OEMed
it, and their firmware doesn't include useful things like persistent
binding. Perhaps you could install native Emulex firmware? Secondly, Windows
2K is really bad at handling tape devices, and even with RSM off and
persistent binding configured there are still circumstances where tape
devices can move to different addresses. Solaris is better at this because
it only maps devices to SCSI addresses when you tell it to. AIX is better
still because it dispenses with the pointless SCSI type addresses and maps a
device directly to a WWPN. Blame Microsoft not Legato.

>
>2) DDS licensing clearly states that you need one DDS license per drive to
>   be shared. For entirely unknown reasons, I need two. As soon as I remove
>   either of the two DDS licenses, I get a log message of one of the two
>   shared devices beeing disabled due to insufficient licensing. We've
>   opened a case with Legato and our distributor for this, but I'd still
>   like to aks whether anyone else has already seen this. Note, it's
>   one physical drive, but two shared (virtual) devices. The need for
>   two DDS licenses contradicts the docs which emphasize intensely on
>   the DDS license to be required per *physical* drive.
Sounds like a bug. FWIW I have successfully implemented DDS on Compaq SAN
kit running W2K. This was about 18 months ago using 6.1.1. It all just
worked. Interestingly at 6.1.1 the DDS licensing didn't seem to be enforced
at all, it worked before I put the licences in.

>
>3) Regarding the somewhat stress sensitive tape pickup mechanism of DLT,
>   I really don't like the fact that DDS requires unloading and instantly
>   reloading the same cartridge to move it between the virtual drives. I
>   don't expect a way around this, as it seems to be designed that way,
>   but I'll ask anyway.
Room for improvement IMO. I don't see why it can't just remap the drive
without unmounting. I also can't see why they need to rely on a timeout to
unmount the drive - surely the NW server can decide to unmount a drive when
it is required for another storage node. This would be far more efficient.

>
>>From the points above, what clearly disturbs me most is 1), as it seems
>that these errors even cause media to be errouneously marked as full.
>Anyone with some insight on this?
I would expect this. Device errors usually cause this and usually it is what
you want, since you may have a case where a drive has been reset and thus
rewound. Writing further data at this point could be disastrous. The answer
is to fix the source of the problem.

HTH.

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