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  • iSCSI question

    From Greg@21:1/5 to All on Mon Sep 16 18:50:02 2024
    Hi there,

    I would like ot use Debian box as iSCSI server (target if I'm not
    wrong). So I have two questions:

    1. If I export /dev/md0 via iSCSI would I benefit from memory buffers?

    2. Is it possible to export a virtual device (like vmdk) by iSCSI? This
    would allow slight overbooking of the storage space.

    Thanks in advance for any help
    Greg

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  • From Arno Lehmann@21:1/5 to All on Mon Sep 16 21:30:02 2024
    Hi Greg,

    Am 16.09.2024 um 18:41 schrieb Greg:
    Hi there,

    I would like ot use Debian box as iSCSI server (target if I'm not
    wrong). So I have two questions:

    1. If I export /dev/md0 via iSCSI would I benefit from memory buffers?

    That's an interesting question... in all environments I ever used it,
    network was the bottleneck, so even if there are scenarios where memory
    buffers may be useful, you'd need very good connectivity to notice them,
    I think.

    2. Is it possible to export a virtual device (like vmdk) by iSCSI? This
    would allow slight overbooking of the storage space.

    vmdk in particular I don't know, but I have exported overcommitted /
    thin LVs; for vmdk you might need to add some fancy losetup wrapper.

    My experience with overcommitting block storage is not purely positive,
    so I'd suggest to be very careful ;-)

    Cheers,

    Arno

    Thanks in advance for any help
    Greg


    --
    Arno Lehmann

    IT-Service Lehmann
    Sandstr. 6, 49080 Osnabrück

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  • From Andy Smith@21:1/5 to Greg on Tue Sep 17 00:20:01 2024
    Hi,

    On Mon, Sep 16, 2024 at 06:41:28PM +0200, Greg wrote:
    1. If I export /dev/md0 via iSCSI would I benefit from memory buffers?

    I've very little experience with iSCSI and don't know the answer to
    this…

    2. Is it possible to export a virtual device (like vmdk) by iSCSI? This
    would allow slight overbooking of the storage space.

    …just want to say that I use qemu-nbd to turn things like vmdk
    images into block devices, which I can then do anything with that I
    do for other block devices, so that might be an option.

    https://jasonmurray.org/posts/2021/mountvmdk/

    Thanks,
    Andy

    --
    https://bitfolk.com/ -- No-nonsense VPS hosting

    Please consider the environment before reading this e-mail.
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  • From Greg@21:1/5 to Andy Smith on Tue Sep 17 10:00:01 2024
    On 9/17/24 00:12, Andy Smith wrote:
    Hi,

    On Mon, Sep 16, 2024 at 06:41:28PM +0200, Greg wrote:
    1. If I export /dev/md0 via iSCSI would I benefit from memory buffers?

    I've very little experience with iSCSI and don't know the answer to
    this…

    2. Is it possible to export a virtual device (like vmdk) by iSCSI? This
    would allow slight overbooking of the storage space.

    …just want to say that I use qemu-nbd to turn things like vmdk
    images into block devices, which I can then do anything with that I
    do for other block devices, so that might be an option.

    https://jasonmurray.org/posts/2021/mountvmdk/

    Thanks for the tip. it seems quite natural idea to use virtual drives.
    Is there any tgtd "plugin" or "driver" with virtual disk support?

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Greg@21:1/5 to Arno Lehmann on Tue Sep 17 09:50:02 2024
    On 9/16/24 21:21, Arno Lehmann wrote:
    Hi Greg,

    Am 16.09.2024 um 18:41 schrieb Greg:
    Hi there,

    I would like ot use Debian box as iSCSI server (target if I'm not
    wrong). So I have two questions:

    1. If I export /dev/md0 via iSCSI would I benefit from memory buffers?

    That's an interesting question... in all environments I ever used it,
    network was the bottleneck, so even if there are scenarios where memory buffers may be useful, you'd need very good connectivity to notice them,
    I think.

    I'm using ConnectX 3pro Mellanox adapters (56Gbps), it was cheaper than
    10Gb Ethernet.

    2. Is it possible to export a virtual device (like vmdk) by iSCSI?
    This would allow slight overbooking of the storage space.

    vmdk in particular I don't know, but I have exported overcommitted /
    thin LVs; for vmdk you might need to add some fancy losetup wrapper.

    My experience with overcommitting block storage is not purely positive,
    so I'd suggest to be very careful ;-)

    Ok, thanks

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)