I've never gotten the WinAoE driver to work with Windows 7, but others claim to have; perhaps someone on the list can help.

We want to run vblade in read only mode for a windows 7 image.  Do you all know if it is possible? We want this virtual drive to be shared by multiple computers?

Thanks.
Angelica

----------------eredeti üzenet-----------------
Feladó: "Alexandre" <alxgomz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Címzett: "PongráczI" <pongraczi-DMSA/VFjocCJhwefxg0Ghb9Ecf289nFAVpNB7YpNyf8@public.gmane.org>
CC: "aoetools-discuss lists.sourceforge.net" <aoetools-discuss-5NWGOfrQmneHXe+LvDLADg@public.gmane.orgrceforge.net>
Dátum: Sat, 6 Apr 2013 10:57:22 +0100
----------------------------------------------------------

Oh are you talking about iSCSI Digest?
 

If so I recommend you read this (only the the chapter should be enough to shced a ligth):
http://www.jdsu.com/ProductLiterature/Understanding-iSCSI-Digests-white-paper-30162803.pdf

 

To make the long story short, iSCSI digest is meant to protect against errors during protocol transitions on the hosts, which are highly used in iscsi ([data]/iSCSI-> TCP -> IP -> Ethernet) while aoe only uses ethernet as a carrier so is far less prone to this kind of error.

 

Moreover, the overhead introduced by digest seems to have lead people to disable it in most cases (most initiators disable it by default, and the document states that it is known to be a common practice in the iscsi world). Instead, integrity is ensured by Etherne qnd IP checksums (whle AoE only needs to check the Ethernet CRC).

 

If you're talking about another mechanism please let us know.
 

Alexandre, thank you for your valuable answer! Good to know, iscsi in practice has a good protection, which commonly disabled, great :)

So, as I checked the Layer2, it has error checking as you wrote. So, as I understand now, data corruption cannot happen on layer2, because this basic CRC protection handle layer 1 issues which can happen in the physical layer.

István

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Feladó: "Alexandre" <alxgomz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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CC: "aoetools-discuss lists.sourceforge.net" <aoetools-discuss-5NWGOfrQmneHXe+LvDLADg@public.gmane.orgrceforge.net>
Dátum: Sat, 6 Apr 2013 10:24:10 +0100
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I am not sure to understand against which type of error you want a protection/detection of.
 

Are you talking about corruption of data during the the transport over the wire?
 

Can you find the name of the feature implemented in iscsi you'd like to check for in aoe?

 

regards, Alex
 

 

Hi,
 

Thank you for your feedback! I try to explain my question in a better way :)

So, your first question is exactly my question: Are you talking about corruption of data during the the transport over the wire? Yes.

On the client side, I want to write to the disk a data, for example a binary data: 01111000001111100001111    I want to be sure, on the server side it will be written to the disk the same data: 01111000001111100001111

At this moment, I do not know, if an electrical noise or whatever will alter the data sent trough the wire, how will layer 2 and AoE handle that situation?

For example I wrote 'piano' on the client, but 'violin' will be written to the disk on the server, due to the corruption during the transport over the wire happens. Is that possible to get this kind of corruption, or layer2+AoE can catch this situation and can fix this kind of issues?

I use ZFS filesystem, it uses end-to-end data protection by using extra checksum to every block written to the disk. This can provide very good data protection, but would be nice to know, using AoE will not cause corruption in a SAN environment. Others, who use iscsi, always tell me, iscsi has checksum to detect transfer issues, while AoE has no this kind of protection, so, to get data corruption can happen and will be not detected. In fact, I never used iscsi, due to that comparing to AoE it is much more complicated and I saw several people had issues to get it running on their environment. AoE just works.

Thank you!

István

For example, 

Dear All,

I use AoE with ZFS in various configuration.

I really like AoE as it is very simple to deploy and working well with ZFS (ZoL).

The only thing, what I cannot answer (after checking the list archive without too much success), is there any solution, how to detect and resend corrupted data over the network?

For example, even if I use zfs on the initiator machine to protect data, it could be corrupted when transferred trough the ethernet and saved the corrupted data. When I will read back, I can detect the corrupted data, but not able to fix it (as zfs do normally when there are enough valid replication of the data).

In contrast, iscsi has this feature and lot of people use iscsi because it provides protection against such an error.

So, my question is are there any solution how to detect/fix these kind of errors?

Sorry, if this question already answered somewhere, in this case please let me know the link :)

Thank you!

István

I don't know much about blade, but have you tried other aoe targets? For instance I know ggaoed have an option to use directIO, thus disabling any caching (and decreasing performance I guess, although I never measured this precisely). This option typically ensure data constancy, which seems to be  what you're trying to achieve.

Hello all,

I`ve tested this software and see, that I can`t turn off write cache. "Write cache off" can be a great feature for use with DRBD or so on.

Recently I`ve tested AOE with DRBD. Everything was working fine, but when I turn off primary server and then start AOE at secondary while writing data - there was data corruption.

iSCSI target has "write cache off" options and data was written correctly.

But as for me, AOE is faster, simplier and Windows client don`t hang while switching vblade from one server to another.

May be somebody can patch sources or tell me another way to turn off write cache?

Looking at the source of vblade-20, I see that this function perform write:

linux.c

....

int
putsec(int fd, uchar *place, vlong lba, int nsec)
{
        return pwrite(fd, place, nsec * 512, lba * 512);
}

....

So need to sync write queue before return?

May be using function

blk_queue_flush(q, REQ_FLUSH | REQ_FUA)

?

If it will be usefull, I can give additional information about versions, testing methods and so on.

PV.