Basic SAN Question...

Oh Man,
I cant believe the level of knowledge about SAN's that exists here.
If I had known I would have defined it in more layman terms

"Bill Todd" wrote in message
...
wrote:
Thanks for the quick response. Does it matter how I copy the data.
For example, mapping a drive or ftp? Say I make a request to copy a
large file from servera to serverb. Servera says I need the data off
the LUN, sends it through the HBA to the FC switch which says hey I
know where that LUN is and sends it to the appropriate LUN. Even
though servera cannot see the LUN for serverb the switch knows where
the LUN is at. Is this correct?

Not unless you're running some very unusual software in both servers and
in the switch and/or the MSA1000: otherwise, the only entities that know
exactly *where* to get the data and *where* to put it are the servers
(and, incidentally, they're also the only ones *allowed* to do things like
that, because there's usually no mechanism to coordinate concurrent
accesses to their file systems with another entity such as the switch),
and since each can see only its own LUN Server a has to obtain the data,
send it (presumably over the LAN) to Server b, which then writes it to its
own LUN.


Sorry if this is a dumb question.

Don't worry: it's already elicited one blatantly incorrect answer, which
places at least some kind of bound on how 'dumb' it can be.

- bill

Ramesh Pun wrote:
Oh Man,
I cant believe the level of knowledge about SAN's that exists here.
If I had known I would have defined it in more layman terms

It seems that your command of English is no better than your
understanding of storage architectu 'layman' is not a synonym for
'accurate'.

- bill

Ramesh Pun wrote:
I guess we need to define what a SAN is then.

No, Nik and others here understand that quite well, thank you.


For me a SAN is all the fabric components (HBA, switch, storage).

The only thing I would correct in that little diagram is make the arrows
double headed.

serverA - SAN - serverB

Now, we can expand the SAN

HBA-serverA - Switch - Storage - Switch - HBA-serverB

Now, the fact that server A and server B cant see each others storage is
secondary.
The config is correct.

Only as far as it goes, which is not far enough to answer the original
question.


If you wanted to copy data from serverA's LUN to serverB's LUN, you dont
necessarily have to go over a LAN link, you could do it with the storage
box.

No, you could not.

If you wanted to copy *the entire contents of servera's LUN to serverb's
LUN* (destroying whatever already happened to be present on serverb's
LUN in the process), then yes, with appropriate snapshot (in case
servera might want continued update access to its LUN during the
operation) and copy support in the storage box, and some interface to
that support, and agreement from serverb that it would leave its LUN
alone while all this was going on you could do so.

But when someone talks about 'copying data' (as distinct from, say,
'copying the LUN') they're usually talking about file-level operations,
and indeed Dave's subsequent response made that very clear.

- bill

"Bill Todd" wrote in message
news
But when someone talks about 'copying data' (as distinct from, say,
'copying the LUN') they're usually talking about file-level operations,
and indeed Dave's subsequent response made that very clear.

- bill


semantics......

I guess what we have established is that theres more than one way to skin
the SAN 'cat'.

"Ramesh Pun" wrote in message

semantics......

I guess what we have established is that theres more than one way to skin
the SAN 'cat'.
But only one of those ways is relevant when answering the original question.
If we are all allowed to redefine the original question to fit whatever
answer we happen give then this is going to become a forum of limited to
value(tm).


--
Nik Simpson

Charles Morrall ) wrote:

: Heck, Fibre Channel is a SCSI-3 protocol.

Technically speaking that is not correct. An analogous and equally incorrect
statement would be "Ethernet is a file storage protocol". FCP is a SCSI-3
protocol that uses Fibre Channel as the underlying network interconnect
just as Ethernet is the underlying network interconnect for NFS.

Dave