OSSV [Open System SnapVault]


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OSSV [Open System SnapVault]

  1. 1. Open System SnapVault OSSVOpen Systems SnapVault is a disk-to-disk backup and recovery solution to protect data residing onnon NetApp storage systems and platforms. This agent-based solution transfers data directly froman OSSV host to a NetApp secondary storage system in the form of block-level incremental backups.These backups are captured as Snapshot™ copies on the NetApp secondary system. The advantage isfast, reliable, space-optimized backups centralized on NetApp technology.What makes OSSV so special is its ability to work at a block level (not a file level). When an OSSVbackup takes place, the client queries the remote system’s filesystem and looks for changed files.Once a list of changed files has been created, the OSSV client then does a block-level comparisonusing block checksums to distinguish which blocks have changed within those files. A copy of thoseblocks is then created and sent to NetApp storage for backup. This is an incredibly efficient way ofperforming backups that requires very little storage space and very little bandwidth in-between thesource and destination.OSSV for Data Migration?OSSV methodology can be used to do data migrations. For example, to migrate Windows share dataon a standalone file server to the NetApp filer. In most situations, professionals use native Windowstools (i.e. robocopy) to migrate this data. A baseline copy would be generated, additionalincrementals may occur up until the respective cutover time (outage window), client access would
  2. 2. be removed, one last incremental update would occur, DNS changes would be made (if necessary),and client access would be restored. This process is simple but time consuming depending upon thesize of the cifs share and the rate of change of data during incremental updates. Traditional tools likerobocopy are file-level utilities. They look for files that have changed based on date/time, archive bit,etc. If a file has changed (even slightly), the file is flagged to be transferred. Imagine having a bunchof large files (1GB+) that change in-between each interval. The time it takes to do each update couldtake a lot longer that one would ever like.Advantage of OSSV over traditional copy tools:OSSV edges other tools when it comes to incremental backups. OSSV incremental backup onlycopies block-level changes. Even though OSSV has to run through the entire directory/file tree onthe source and look for changed files. The difference comes in the data transfer time.OSSV will ONLY send changed blocks to the NetApp. If you are migrating a bunch of large files, thismethod will considerably cut-down on data transfer time.The basic components that make up OSSV architecture are as follows:  OSSV host (Windows/UNIX based)  OSSV agent software  NetApp Host Agent  TCP/IP network  NetApp storage system  DFM (OnCommandCore): This is optional, in case you want to manage backup and restore from central location.Let’s run through this process step-by-step:1. Download and install the OSSV client on the source host (an existing Windows file servercontaining data that you want to move to CIFS or NFS shares on a NetApp). See the Open SystemsSnapVault Installation and Administration Guide for further information. Please see the last page forreference material.2. During OSSV installation, be sure to add the destination NetApp to the QSM Access List in order toallow SnapVault to gain access to the source data. SnapVault is a “pull” replication technology. Thebaseline transfer and all updates are initiated by the destination NetApp. If you forget to performthis step during install, you can go back within the OSSV Configurator on the host and edit thesettings there. The QSM Access List is under the SnapVault tab of the OSSV Configurator.
  3. 3. 3. Verify that the following licenses exist on the destination NetApp FAS array: sv_ontap_sec andone of the following dependent on the source OS (sv_windows_pri, sv_linux_pri, sv_unix_pri, orsv_vi_pri)4. On the destination NetApp, create a new volume with enough space to hold the data to bemigrated.5. Make sure SnapVault is enabled on the destination NetApp:snapvault status; options snapvault.enable on6. Kick-off a baseline transfer using the following command:snapvault start -S [source_hostname]:[source_path] [dest_path]Ex:snapvault start -S fileserver: C:myshares /vol/fileshares/mysharesNote how you need to specify the name of a new qtree in the destination path. This qtree is createdas part of the SnapVault initialization. There is no need to create this ahead of time.7. Check status of the new SnapVault relationship and wait for the baseline to complete:snapvault status8. You’ll probably want to continue running incremental updates to the destination NetApp prior toperforming a cutover. This can be done manually using the following command. You could also usethe NetApp PowerShell Toolkit and create a PowerShell script and subsequent Windows ScheduledTask to run this automatically (a topic of discussion for a later date).snapvault update [destination_path]Ex:snapvault update /vol/fileshares/myshares9. Schedule a maintenance window to perform the cutover from the Windows file server to theNetApp. How long of a maintenance window should be determined based on how long yourincremental SnapVault updates are taking plus additional time for prep, check, and test tasks.10. At the time of the maintenance window, start by removing access to the source file server inorder to prevent any data changes from being made. On a Windows file server, you’re best bet is tojust stop the Server service. Once you have removed user access, kick-off a SnapVault update on thedestination NetApp (see step 8). Let this complete. Once completed, rename the source Windowsfile server’s hostname. The NetApp will be assuming this hostname so that users will not have tomake any changes to UNC paths in order to access their shares. If you’re changing the hostname of aWindows file server that is joined to an Active Directory domain, a reboot will be necessary for thechange to be made. Once the old file server has been rebooted, go into your internal DNS and createa new CNAME record. The new CNAME record should use the hostname of the old Windows file
  4. 4. server and point to the hostname of the NetApp. (NOTE: This assumes that the destination NetAppwas previously configured for CIFS and joined to your Active Directory domain).11. Validate that you can access shares on the NetApp using the old hostname. You may need toperform a DNS flush on your workstation in order to resolve the old hostname with the new IPaddress of the NetApp.12. Once you have validated access, you’ll need to convert the SnapVault destination volume on theNetApp to a read/writable volume. SnapVault destinations are always read-only and cannot be maderead/writable without additional configuration. This process is documented in the NetApp KB articleprovided at the end of this article.The process of converting a SnapVault destination to a read/writable volume can take a few minutesto complete. The bulk of the conversion time occurs during the SnapMirror break process. This cantake upwards of an hour depending on the model of controller used to perform this operation.13. Bring over your CIFS shares. Depending on the number of shares that existing on the Windowsfile server, you could either migrate the shares manually or via the use of scripts. One can do a ‘netshare’ dump from the Windows file server, copy that output to an Excel spread sheet, and then usethat data to create ‘cifs shares -add’ commands on the NetApp console. Validate that all shares havebeen copied over and you can access all of them on the NetApp. You can use ‘cifs sessions’ tovalidate your connectivity to the NetApp.Backup & Restore are based on Technology.SnapVault is a “pull” replication technology. The baseline transfer and all updates are initiated bythe destination NetApp. SnapVault use TCP port 10566 for data transfer. Network connections arealways initiated by the destination system; that is, SnapVault pull data rather than push data.How does OSSV actually transfer data from primary to secondary system?Data is moved via TCP/IP network using TCP port 10566. The communications protocol is QSM(based on Qtree-SnapMirror). This is not to be confused with NDMP protocol. NDMP (TCP port10000) is used by NDMP-based management applications (ex- DFM/OnCommandCore) formanagement and control of the SnapVault primary and secondary systems. Actual data transferhappens over TCP port 10566.
  5. 5. Where can I locate QSM TCP port 10566 during BACKUP & RESTORE?This port can be located at the point of –‘Data Retrieval’. For ex –During BACKUP: 10566 is located at OSSV HostDuring RESTORE: 10566 is located at FILERDuring idle state: OSSV host listens on following ports. TCP win2k8ossv:0 LISTENING[ntap_agent.exe] TCP win2k8ossv:0 LISTENING[svlistener.exe] TCP win2k8ossv:0 LISTENING[svlistener.exe]During idle state: DFM Server host listens on following ports. HTTP: TCP win2k8R2:47065 ESTABLISHEDHTTPS: TCP win2k8R2:47065 ESTABLISHED [dfmserver.exe]What exactly happens during OSSV RESTORE?When you kick-in Restore from DFM server and do netstat -abnp tcp’, you can see DFM servertalking to both OSSV and Filer on NDMP port 10000 via DFPM (Protection Manager Module).Note: Both NDMP Port 10000 remains active until the restore is complete. TCP[DFM] (OSSVhost) ESTABLISHED[dfpm.exe] TCP[DFM] (FILER) ESTABLISHED[dfpm.exe]
  6. 6. 1. DFM server sends restore request to Filer.NDMP connection (restore request) accepted from (DFM)TCP[DFM] 10000[FILER] ESTABLISHED[dfmserver.exe]2. OSSV host connects to Filer and establishes connection.QSM Server connected to machine on port 10566 (Filer)TCP[OSSV][FILER] ESTABLISHED[qsmserver.exe]3. OSSV host begins pulling the data across from the filer.fas01> netstat -aActive TCP connections (including servers)Local Address Remote Address Swind Send-Q Rwind Recv-Q State192. [FILER][OSSV] 4202496 2089152 7340880 0ESTABLISHEDwin2k8ossv:C:luckjre-7u6-windows-x64.exe: Source - Transferring (OSSV_host)4. Data is fully restored to the OSSV host.Restored data from /vol/ossv_new/Cxxluck/netapp.snapdrive.linux_5_1.rpm toC:/luck/netapp.snapdrive.linux_5_1.rpm via default interface5. Releases the snapshot used by the restore.Released snapshot used by the restore of/vol/ossv_new/Cxxluck/netapp.snapdrive.linux_5_1.rpm
  7. 7. 6. Finally, releases the relationship used by the restore.Released relationship used by the restore of/vol/ossv_new/Cxxluck/netapp.snapdrive.linux_5_1.rpm7. Restore Ends.Successfully restored path using SnapVault RestoreWhat exactly happens during OSSV BACKUP?When you kick-in Backup from DFM server and do netstat -abnp tcp’, you can see DFM servertalking to Filer & OSSV host on NDMP port 10000 via DFPM.Note: Once backup relationship is established, DFM is no longer talking to OSSV host, and you canactually see port 10000 no longer listening on OSSVhost after few seconds/minute. At times, youmay not see this port established on OSSV Host during Backup at all.1. DFM server sends backup request to Filer & also talks to OSSV host for creating a base-linerelationship. TCP[FILER]:10000 ESTABLISHED[dfpm.exe] TCP[OSSV-HOST]:10000 ESTABLISHED[dfpm.exe]2. Filer connects to the OSSV host on QSM interface and establishes connection.TCP[FILER]:14764[OSSV-HOST]:10566 ESTABLISHED[svlistener.exe]3. Filer initiates the backup by pulling the data from OSSV host as shown in the netstat output below.fas01> netstat -aActive TCP connections (including servers)Local Address Remote Address Swind Send-Q Rwind Recv-Q State192. [FILER] [OSSV-HOST] 65280 0 27 7340853ESTABLISHED
  8. 8. Issue faced during RESTOREOSSV is fairly easy setup and one should expect to perform Backup & Restore without any issues aslong as Port 10000 & 10566 is opened at the firewalls.At my customer site, Backup worked smoothly but every time we tried to do restore it just won’tobey. Following error was seen:Error:Connection had exception. Failed to connect to filerI cracked my head for a week (almost frustrated) to get around this issue but with no luck. I finallydecided to do ‘netstat –abnp tcp’ on OSSV Host while running Restore and this is where I discoveredthe following:Symptoms:TCP [OSSV] 52202 [FILER]:10566 SYN_SENT[qsmserver.exe]Basically, TCP connection was never established, Host never received SYN, ACK Packet back.This was also captured in the pktt trace I ran between OSSV Host & Filer. At this point I knew SYNpackets are being sent but ignored at the FILER end. I finally decided to open a case with NetAppSupport.Solution:NetApp Support discovered that the ‘snapvault interface’ was listed in the snapmirror blockedinterface list on the filer. Removing the interface from this list solved the issue.Filer>options interface.blocked.snapmirrorTherefore, SYN packets on port 10566 were ignored.On the side note, I think packet tracing is quite an invaluable tool when it comes to dealing withissues on TCP/IP network, it can almost tell you what’s wrong, if not how to fix it. I guess, you learnthese skills with experience.
  9. 9. Document reference:OSSV Installation and Admin Guide: 3.0.1https://support.netapp.com/documentation/docweb/index.html?productID=61032Installation and administration Guide: Part No. 215-05638_C0OSSV Best Practices Guide:http://media.netapp.com/documents/tr-3466.pdfOnCommand Core 5.1 :( DFM)Guide to Common Provisioning and Data Protection Workflows for 7-Mode: Part No. 210-05421_A0Note: You need a support account to access this knowledge resource. To login go tohttp://support.netapp.com/How to release a SnapVault relationship and make the secondary qtree writable (Useful: Whenyou are doing Data Migration using OSSV, rather than robocopy or any other CIFS copy tools)https://kb.netapp.com/support/index?page=content&id=1010906Courtesy:http://waflhouse.com/?p=12 -Prepared by Ashwin Pawar ashwinwriter@gmail.com