[ENBD] Even more on 2GB Limits... Huh...

[Kai Chen]

Hi! Peter,

>I see. Well, I would guess that something in the driver has 32 bits
>where it should have 64. Try and find out where the observed limit
>comes from by varying the setup, removing or adding one element at a
>time.

I can create >2GB partitions on the logical volumes on these SCSI devices 
presented by the Qlogic card.  Doesn't that mean the qlogic driver is OK?  I 
don't have any local device that can provide such a large space at this 
point, so I will need a new hard drive to do what you suggested....  Well I 
will keep trying and let you know what I find.

>But merge_requests=0 is the makefile default (and is sure death in
>2.2.18 if missed). And it seems to be the compiled-in default if
>one doesn't say anything too. So I don't see how it can be involved.

I couldn't get NBD 2.2.* to work at all.  I was using NBD 2.4.20 and NBD 
2.4.21 with kernel 2.2.18.  I suppose your default for merge_requests might 
have changed for those newer NBD (2.4.*)?

I'm positive about "merge_requests=0 + mount -o sync" making it work at last 
(NBD 2.4.21 + Kernel 2.2.18).

>>Yes.  I do have LVM, and it is a patch for 2.2.18.  I just haven't run it 
>>with NBD yet.
>
>Run it or applied it? Applying a patch is sufficient to alter your
>kernel in many ways (if you compile it :-).

Well I did apply the patch and compile a new kernel with LVM support.  I 
don't think it will present a problem for NBD, right?

>It shouldn't. There is no limit in the block layers in the kernel,
>2.2.18 or 2.4.0. There is a limit in the FS codes in 2.2.18.

It's good to know that.

I checked the old archive, and I saw somebody was comparing DRBD with ENBD.  
I think DRBD is somewhat like ENBD + "networked RAID 1."  Could you comment 
on that?  I plan to build an HA NBD cluster, and I intend to use ENBD.  I'd 
like to learn your view on this issue.

Thanks a million.

Kai
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