Data Protection Software

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  • 1.  FCTOOL and LVM causing trouble

    Posted Wed January 05, 2022 01:44 PM
    Hello, it is my first time using FCtool to interact between SAP HANA and a Flash System. So far flashcopy backups are running successfully, but when I try to use the copy function to clone one system to another one, I am getting trouble with LVM in the target system. FlashCopy consistency group is created as well as flashcopy relationships. Once the flashcopy has ended, I can see in the Flash System that target flashcopy volumes are attached to the target system but when the fcagent tries to activate the VG it reports errors because of duplicated PV ids. After talking to the Linux expert, he tells me that the duplicated PVs are pointing to the same device because of the use of LVM. 

    Any help will be thank. I am completely lost. 



  • 2.  RE: FCTOOL and LVM causing trouble

    Posted Thu January 06, 2022 03:36 AM
    Hi Maria, as sent via email, please be so kind and send me the trace files.
    I assume the other LINUX system you want to copy HANA to is "empty", does not have any HANA system yet ?
    Thanks, Markus

    Markus Fehling

  • 3.  RE: FCTOOL and LVM causing trouble

    Posted Sun January 09, 2022 05:20 AM
    Hi Markus, I sent the log file and fctool.ini in an email.

    The target system now is empty, originally it was not. I talked to the customer to warn him that data and log file systems, vgs and pvs should be removed from that system and they detached them. One of the executions of the copy process was done while the data and log LUNs were still attached in the disk storage subsystem to the target system, but I detached them and run the copy process again. Currently the situation is that flashcopy target volumes are attached to the target system, but when the copy process tried to activate volume groups (hanadatavg and hanalogvg), the process failed because of duplicated PVs. These duplicated PVs in fact are only one, but the system can see them through multiple paths using multipath and this is the reason because the process failed.


  • 4.  RE: FCTOOL and LVM causing trouble

    Posted Fri January 07, 2022 05:03 AM
    Hi Maria,

    These PV conflicts you have, can these be minor major related?
    It is common to encounter LVM disk conflicts using snapshot techniques, where special attentions has to be done with the minor major numbers, to avoid such conflicts.
    Perhaps you can try exporting / importing the vg, to resolve the issues?

    At spictera we created a way to take software based snapshots, which does not have such conflicts.
    The snapshots are stored on the IBM Spectrum Protect backup server, and does not require a special hardware.
    The total number of retentions is limited to what you set in the Spectrum Protect backup server retention policy, and are not limited to what the hardware can support.
    The snapshot can be provisioned back to any location, at any time, using same or new structure.
    The snapshot revert to previous snapshot using normal OS snapshot revert mechanism.

    IBM - Spictera Brick - Instant Recovery for Spectrum Protect

    Regards Tomas

    Tomas Dalebjörk

  • 5.  RE: FCTOOL and LVM causing trouble

    Posted Sun January 09, 2022 05:25 AM
    Hi Tomas, we can import or export the volume group because when the copy process detects it can't activate the volume group because of the duplicated PVs, starts a removevg command and the volume group is removed. 

    Linux OS expert thinks that the problem is related to multipath, because the PVs reported as duplicated are in fact the same PVs but seen through different paths using multipath. But I don't know whether there is a way to configure multipath to avoid these errors trying to activate the VGs.



  • 6.  RE: FCTOOL and LVM causing trouble

    Posted Mon August 28, 2023 03:47 PM

    It sounds like you are encountering issues related to LVM (Logical Volume Manager) when trying to clone one SAP HANA system to another using FlashCopy technology. The error you're facing with duplicated PV (Physical Volume) IDs is indeed related to LVM configuration and device mapping. Let's break down the steps to address this issue:

    Understand the Problem:
    The duplicated PV IDs occur when LVM in the target system detects PVs with the same unique identifiers as the source system. This is usually because the FlashCopy process clones the entire storage, including the PV metadata.

    Unique Identifier for PVs:
    Each PV in LVM has a unique identifier stored in its metadata. When you clone storage, these identifiers can get duplicated, causing LVM to see multiple PVs with the same ID.

    Steps to Resolve:

    a. Change PV IDs: Before activating the VG (Volume Group) in the target system, you need to change the PV IDs to make them unique. You can use the pvchange command with the -u option to set a new unique ID for each PV.

    b. Activate VG: After changing the PV IDs, you can activate the VG using the vgchange command.

    c. Update Configuration: Make sure to update your configuration files, such as /etc/fstab and any custom scripts, to reflect the new PV IDs.

    d. Reboot Consideration: It's often recommended to reboot the system after changing PV IDs to ensure that all changes are applied properly.

    Best Practices:

    a. Pre-Clone Preparation: Before initiating the FlashCopy, consider preparing the target system by removing LVM metadata, VGs, and PVs. This prevents the duplication issue from occurring in the first place.

    b. Backup and Test: Ensure you have backups of critical data before making changes to PV IDs or performing any other actions.

    c. Consultation: Given the complexities involved, it's advisable to consult with your Linux expert or a storage specialist to ensure the correct steps are taken for your specific environment.

    d. Vendor Documentation: Check the documentation provided by your storage array vendor. They might have recommendations or tools to handle these scenarios more efficiently.

    Remember that working with storage-level operations like FlashCopy and LVM requires careful planning and consideration. Mistakes can lead to data loss or system instability. If you're not confident in handling these operations, consider involving professionals who are experienced with both SAP HANA and the underlying storage infrastructure. 

    big redd

  • 7.  RE: FCTOOL and LVM causing trouble

    Posted Mon August 28, 2023 04:39 PM

    This will never happen using Spictera Unified Storage, where the snapshots are stored on the IBM Storage Protect as the snapshot disk is provisioned internally using unique LUN id and associated to any lvm volume as a snapshot.

    Tomas Dalebjörk