If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
I am new to this SAN stuff as we just got a CX500 and CX300 installed by
Dell. I am trying to get my arms around the SANCopy, Clone and Snapshot concepts. I know that they are different but I don't know how. Can someone explain them to me? The way I understand it is if I did a "Clone" of a source LUN from the CX500 to the CX300 at a DR site I would have an exact copy of the source LUN. (i.e. If the source LUN had 500GB of data so would the "clone" LUN). So what happens if I did a SANCopy of that same LUN to that same remote LUN? Wouldn't it still be 500GB? So what's the differance? And what will Snapshots do for me? We also have a mount host at the DR site. We have two Exchange 2003 clusters on the SAN and two Windows 2000 file server hosts connected to the SAN right now. Thanks for any input, Clayton |
#2
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
Clayton,
Clone is within the same array. You can't "clone" to a different array. You use MirrorView for that purpose. SANCopy is (typically a one-time operation) used to copy bulk data from a Clariion to another storage array (target doesn't have to be a Clariion). Snapshots are point in time copy of the source lun. Once you take a snapshot and activate it, any changes made to the original source lun are tracked in a special lun called cache or reserve lun. The cache lun is typically 10-15% of the source lun and holds the blocks that have been changed in the original lun. HTH |
#3
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
Thanks for your reply Madhu,
Okay, I think I understand the Clone (and MirrorView) concept. You would use it when you wanted another copy of you data on-site. But if you want to push a copy off-site (maybe to a DR site) then your would have to use SANCopy. Do I have that right? But what do you mean the SANCopy is "typically" a one time operation? If you are using SANCopy don't/can't you use it to schedule a SANCopy nightly if you want? SnapShots - Okay, I can relate to most of that. But, if the original sourse LUN changes and the changes are tracked in the cache LUN when is it written to the source or Snapshot? Thnaks for all of your help, Clayton wrote in message ups.com... Clayton, Clone is within the same array. You can't "clone" to a different array. You use MirrorView for that purpose. SANCopy is (typically a one-time operation) used to copy bulk data from a Clariion to another storage array (target doesn't have to be a Clariion). Snapshots are point in time copy of the source lun. Once you take a snapshot and activate it, any changes made to the original source lun are tracked in a special lun called cache or reserve lun. The cache lun is typically 10-15% of the source lun and holds the blocks that have been changed in the original lun. HTH |
#4
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
Hey HVB,
Thanks for your input. Rather than beat about the bush with the possible merits of various functions, can you tell us what you're trying to do with your storage? Here is what we are trying to do. In our data center we have a CX500 and a Disk Array Enclosure fully populated with disk. We have two Exchange 2003 clusters and two file servers on this SAN for now. We have EMC Replication Manager/SE , SANCopy and SnapView. At our DR site we have another SAN that has an CX300 with a Disk Array Enclosure fully populated with disk (same amount of disk space that's on the data center SAN). The idea when we bought all of this was to "push" in some fashion, our production data to the DR site. Dell came in and set all of this up but didn't do a knowledge transfer so we are kinda left to figure out how all of this works. We are trying to understand and figure the best way to get the data to the DR site (EMC Replication Manager/SE , SANCopy, SnapView or MirrorView) However, we didn't buy "MirrorView" so that's not really an options for us I guess. Dell set up "Replication" jobs for all of the data transfer and ran the jobs as a test once. After that they said we could setup what ever schedule we wanted. We also have a "Mount Host" at the DR site. It is part of the AD domain and just has Windows 2003 and EMC Replication Manager/SE on it. It is also connected into the SAN. So I just need some "ideas" on how to do what we want to do. I am trying to understand the difference between SANCopy, SnapView and MirrorView and when I should use which. Thanks a bunch for all of your help, Clayton "HVB" wrote in message ... On Wed, 04 Jan 2006 00:54:56 GMT, "Clayton Sutton" wrote: Okay, I think I understand the Clone (and MirrorView) concept. You would use it when you wanted another copy of you data on-site. That's what MirrorView does, yes. A clone is like MirrorView, in that it's a complete copy of the source LUN, but the data is copied to a new LUN within the same array. But if you want to push a copy off-site (maybe to a DR site) then your would have to use SANCopy. Do I have that right? Maybe... But what do you mean the SANCopy is "typically" a one time operation? If you are using SANCopy don't/can't you use it to schedule a SANCopy nightly if you want? Typically you'd use SANCopy to push data off an (old) array onto a (new) EMC Clariion. The idea generally being that you'd stop using the old array. Note that with SAN Copy you can move data from selected non-EMC arrays to a Clariion and vice-versa. You'd only use this regularly if you wanted to push data to/from a non-EMC array. This could be scheduled if you wanted. To relate back to your example, you *could* use SAN Copy to push data to a non-EMC array at a remote location (like a DR centre). If you have two similar EMC arrays (i.e. two Clariions) we'd expect to use MirrorView to push the data between the arrays. The exception to this is if you're using EMC Replication Manager/SE to create application-level (Exchange or SQL) replication groups - in that case you *might* use SAN Copy. == note this is fairly unusual and there are other (EMC) ways of doing Exchange/SQL replication. SnapShots - Okay, I can relate to most of that. But, if the original sourse LUN changes and the changes are tracked in the cache LUN when is it written to the source or Snapshot? With SnapShots changes are always written to the source LUN. The old data from the source is written into the 'cache' LUN, really known as the 'reserved LUN pool' HVB |
#5
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
HVB ) wrote:
: SnapShot = *virtual* point-in-time copy of your source volume/LUN. The : size overhead for a snapshot depends on the rate of change of data in : your source volume/LUN. A high change rate will consume more disk : space than a low change rate. When snapshots are made is any effort made to ensure that the snapshot is started at a point where the file system on that LU is in a consistent state? If not, it seems like the snapshots carry a risk associated with them that when a problem is detected the file system may not guaranteed to be in a consisten state on some (and worst case all) of the snapshots. If it does ensure the file system is in a consistent state then how does it detect this? Dave |
#6
|
|||
|
|||
EMC SANCopy, Clone, Snapshot question
Microsoft's VSS (Volume Shadow Service) solves this by notifying the VSS
aware apps (MSSQLServer, Exchange, some Windows-embedded database engines) that the snapshot is about to be created. For instance, SQL server can do the checkpoint and stall all disk writes before snapping, and continue normal work after snapping. Without the VSS-aware snapshot engine (and VSS-aware apps), the write inactivity timeout is the only way. -- Maxim Shatskih, Windows DDK MVP StorageCraft Corporation http://www.storagecraft.com "Dave Sheehy" wrote in message ... HVB ) wrote: : SnapShot = *virtual* point-in-time copy of your source volume/LUN. The : size overhead for a snapshot depends on the rate of change of data in : your source volume/LUN. A high change rate will consume more disk : space than a low change rate. When snapshots are made is any effort made to ensure that the snapshot is started at a point where the file system on that LU is in a consistent state? If not, it seems like the snapshots carry a risk associated with them that when a problem is detected the file system may not guaranteed to be in a consisten state on some (and worst case all) of the snapshots. If it does ensure the file system is in a consistent state then how does it detect this? Dave |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Software to clone disk and resize target partiions at same time? | Bob | Storage (alternative) | 27 | December 28th 05 10:43 PM |
What do you use for backup today? | Mxsmanic | Homebuilt PC's | 46 | July 18th 05 09:19 PM |
couple of Dimension XPS Gen4 question | Matt | Dell Computers | 3 | March 4th 05 02:20 AM |
Question: Reliability of physical snapshots on SANs | Erik H. | Storage & Hardrives | 3 | October 29th 04 04:31 PM |
Question - Printing 2-up on 11x17 | Don | Printers | 1 | August 24th 03 04:27 AM |