Basic SAN Question... - Storage

This is a discussion on Basic SAN Question... - Storage ; I am trying to settle an argument at the office and I am hoping that one of you can answer the question for me. It is fairly basic as I am new to this whole SAN thing. Suppose that I ...

+ Reply to Thread
Results 1 to 17 of 17

Thread: Basic SAN Question...

  1. Basic SAN Question...

    I am trying to settle an argument at the office and I am hoping that
    one of you can answer the question for me. It is fairly basic as I am
    new to this whole SAN thing.

    Suppose that I have two windows servers, each connected to a sepearte
    LUN on an MSA1000 (each server can see his LUN but not the other
    servers). Both servers and the disk are connected to a SAN switch.

    Suppose I want to copy data from the SAN LUN on servera to the SAN LUN
    on server b.

    Does it work this this
    servera -> SAN -> serverb

    or
    servera -> SAN -> LAN -> serverb

    What data goes over the LAN and what goes over the SAN?

    Thanks
    Dave


  2. Re: Basic SAN Question...

    it work this this
    servera -> SAN -> serverb


    wrote in message
    news:1118793314.637893.15960@f14g2000cwb.googlegro ups.com...
    >I am trying to settle an argument at the office and I am hoping that
    > one of you can answer the question for me. It is fairly basic as I am
    > new to this whole SAN thing.
    >
    > Suppose that I have two windows servers, each connected to a sepearte
    > LUN on an MSA1000 (each server can see his LUN but not the other
    > servers). Both servers and the disk are connected to a SAN switch.
    >
    > Suppose I want to copy data from the SAN LUN on servera to the SAN LUN
    > on server b.
    >
    > Does it work this this
    > servera -> SAN -> serverb
    >
    > or
    > servera -> SAN -> LAN -> serverb
    >
    > What data goes over the LAN and what goes over the SAN?
    >
    > Thanks
    > Dave
    >




  3. Re: Basic SAN Question...

    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?

    Sorry if this is a dumb question. I just want to make sure that I have
    it.

    Thanks Again
    Dave


  4. Re: Basic SAN Question...

    dave_roland_mann@yahoo.com 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

  5. Re: Basic SAN Question...


    skrev i meddelandet
    news:1118793314.637893.15960@f14g2000cwb.googlegro ups.com...
    >I am trying to settle an argument at the office and I am hoping that
    > one of you can answer the question for me. It is fairly basic as I am
    > new to this whole SAN thing.
    >
    > Suppose that I have two windows servers, each connected to a sepearte
    > LUN on an MSA1000 (each server can see his LUN but not the other
    > servers). Both servers and the disk are connected to a SAN switch.
    >
    > Suppose I want to copy data from the SAN LUN on servera to the SAN LUN
    > on server b.
    >
    > Does it work this this
    > servera -> SAN -> serverb


    No.
    >
    > or
    > servera -> SAN -> LAN -> serverb
    >

    Yes.

    > What data goes over the LAN and what goes over the SAN?
    >

    All data goes across the LAN. Nothing goes over the SAN as I think you mean
    it, but of course the data gets transferred to/from each server across the
    LAN and then to/from the MSA1000 over the SAN.

    All the SAN is that you have (meaning you probably don't have any
    third-party software or filesystem or some such) is a SCSI bus on a network.
    Heck, Fibre Channel is a SCSI-3 protocol.

    > Thanks
    > Dave
    >




  6. Re: Basic SAN Question...

    dave_roland_mann@yahoo.com wrote:
    > I am trying to settle an argument at the office and I am hoping that
    > one of you can answer the question for me. It is fairly basic as I am
    > new to this whole SAN thing.
    >
    > Suppose that I have two windows servers, each connected to a sepearte
    > LUN on an MSA1000 (each server can see his LUN but not the other
    > servers). Both servers and the disk are connected to a SAN switch.
    >
    > Suppose I want to copy data from the SAN LUN on servera to the SAN LUN
    > on server b.
    >
    > Does it work this this
    > servera -> SAN -> serverb
    >
    > or
    > servera -> SAN -> LAN -> serverb
    >
    > What data goes over the LAN and what goes over the SAN?
    >
    > Thanks
    > Dave
    >



    Think of the SAN as a very complex IDE or SCSI cable.
    Now think of the LUN's in your SAN as an IDE or SCSI disk drive on that
    cable.

    For your scenario above it's the same as transferring data from an
    internal disk on one PC to an internal disk on a second lan attached PC.
    There is no way for the first PC to see the hard disks in the second PC
    without going through the LAN and OS.


    Note this is not the case in Clustering where 2 or more hosts are
    attached to the same LUN for failover. But I don't think this is where
    you were headed.
    There does also exists Snap copies and mirroring and other such
    functions to copy LUNs across the SAN but afaik these are not used on a
    file level, but on a LUN level.


    So let's see if I can draw your scenario.

    ServerA attached to LUN-A, OS calls it the D: drive
    ServerB attached to LUN-B, OS calls it the G: drive

    ServerA maps a drive across the LAN to ServerB's G: drive calling it E:

    On ServerA you xcopy a file from D: to E: and this is the path it takes:

    LUN-A -> SAN -> ServerA -> LAN -> ServerB -> SAN -> LUN-B


    FWIW, here's what happens with a LUN mirror/copy which is a function of
    your SAN's storage processor.

    ServerA attached to LUN-A, OS calls it the D: drive
    ServerB attached to LUN-B, OS calls it the G: drive

    A LUN mirror/copy is initiated to mirror LUN-A to LUN-B. This data
    transfer is done over part of the SAN(inside the SAN's storage
    processor). When it's completed, and provided there has been no IO to
    the source and destination LUNs, ServerA's LUN-A and ServerB's LUN-B
    will be identical. Effectively you've copied data across the SAN.

    So data flows like this:

    LUN-A -> Storage Processor -> LUN-B

    Snap images are similar, but the snap image is an array of pointers to
    the source data for reading vs. full IO. Takes up less space than a
    full mirror of a LUN.

    ServerA attached to LUN-A, OS calls it the D: drive
    ServerB attached to LUN-B, OS calls it the G: drive

    LUN-B is a snap image of LUN-A instead of a separate LUN.

    On ServerB you copy a file from G: to a local C: drive and the data
    flows like this:

    LUN-A -> Storage Processor -> SAN -> ServerB -> Local disk C: on ServerB

    Effectively you've copied data from ServerA's LUN-A to ServerB without
    going over the LAN.

    hth,
    tM




  7. Re: Basic SAN Question...

    I think you have it wrong- it doesn't use the switch per se, it uses the
    LAN- it would be the sanme as copying it from one server to another that was
    NOT SAN attached.

    Personally, I jus copy from server to server, I don't use FTP. But that's
    just me. You aren't getting any more eprformance copying from san disk to
    san disk than if you were copying local to local.

    --
    Kat
    MCDBA # ? of Millions

    What woud you do for a Kit Kat bar?
    wrote in message
    news:1118802026.448555.273660@z14g2000cwz.googlegr oups.com...
    > 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?
    >
    > Sorry if this is a dumb question. I just want to make sure that I have
    > it.
    >
    > Thanks Again
    > Dave
    >




  8. Re: Basic SAN Question...

    FTP is much faster then SMB/CIFS while copying major amounts of data from
    the server to the server.

    --
    Maxim Shatskih, Windows DDK MVP
    StorageCraft Corporation
    maxim@storagecraft.com
    http://www.storagecraft.com

    "Kat" wrote in message news:42b08b5e$1@obsidian.gov.bc.ca...
    > I think you have it wrong- it doesn't use the switch per se, it uses the
    > LAN- it would be the sanme as copying it from one server to another that was
    > NOT SAN attached.
    >
    > Personally, I jus copy from server to server, I don't use FTP. But that's
    > just me. You aren't getting any more eprformance copying from san disk to
    > san disk than if you were copying local to local.
    >
    > --
    > Kat
    > MCDBA # ? of Millions
    >
    > What woud you do for a Kit Kat bar?
    > wrote in message
    > news:1118802026.448555.273660@z14g2000cwz.googlegr oups.com...
    > > 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?
    > >
    > > Sorry if this is a dumb question. I just want to make sure that I have
    > > it.
    > >
    > > Thanks Again
    > > Dave
    > >

    >
    >




  9. Re: Basic SAN Question...


    wrote in message
    news:1118793314.637893.15960@f14g2000cwb.googlegro ups.com...

    > Does it work this this
    > servera -> SAN -> serverb
    >
    > or
    > servera -> SAN -> LAN -> serverb
    >
    > What data goes over the LAN and what goes over the SAN?



    With two servers each mounting their respective LUNs as local filesystems
    there is no way for the basic OS to perform anything other than:

    Lun1(SAN)->Server A ->CIFS/NFS-> Server B -> Lun2(SAN)

    Direct SAN to SAN copy would require a block level copy and would be done in
    the array.


    --
    Nik Simpson



  10. Re: Basic SAN Question...


    "Ramesh Pun" wrote in message
    news:11av1k25a2no21@corp.supernews.com...
    > it work this this
    > servera -> SAN -> serverb


    And just what mechanism in the OS would that happen, inquiring minds want to
    know.


    --
    Nik Simpson



  11. Re: Basic SAN Question...

    I guess we need to define what a SAN is then.

    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.

    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. HP has business copy, EMC has time finder, I am sure IBM has some other
    technology as well.



    "Nik Simpson" wrote in message
    news:Ah2se.90515$lQ3.88937@bignews5.bellsouth.net. ..
    >
    > "Ramesh Pun" wrote in message
    > news:11av1k25a2no21@corp.supernews.com...
    >> it work this this
    >> servera -> SAN -> serverb

    >
    > And just what mechanism in the OS would that happen, inquiring minds want
    > to know.
    >
    >
    > --
    > Nik Simpson
    >




  12. Re: 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
    news:wZKdnccM18SABTLfRVn-uw@metrocastcablevision.com...
    > dave_roland_mann@yahoo.com 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




  13. Re: Basic SAN Question...

    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 architecture: 'layman' is not a synonym for
    'accurate'.

    - bill

  14. Re: Basic SAN Question...

    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

  15. Re: Basic SAN Question...


    "Bill Todd" wrote in message
    newsKudnVWL2_u61C_fRVn-3Q@metrocastcablevision.com...

    > 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'.



  16. Re: Basic SAN Question...


    "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



  17. Re: Basic SAN Question...

    Charles Morrall (charles.morrall@telia.com) 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


+ Reply to Thread