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We have decided to pick two servers (hardware) and dedicate them to kvm virtualization, replicating data from server A to server B using DRBD + LVM (every guest will store its virtual disk into its own LVM Logical Volume).

I've heard that, for the purpose of virtualization, is better to have a dedicated disk with a dedicated host adapter for every virtual machine in order to optimize I/O performance. So should we buy a server with many SSD, host adapter and connectors? ( each SSD will be a LVM logical volume, this way we can expand it attaching a second SSD if necessary).

As an hardware noob my main doubt is: buying a server with many connectors e.g.:SATA will necessarily mean that every SSD will use its own host adapter to moving data back and forth?

Or we have to be careful because multiple SSD slots does not mean necessarily multiple host adapter?

Thank you for the clarification, and for any additional hardware tip related to virtualization

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  • No, unless you have a very special edge case, you don't assign a a dedicated disk and host adapter for each virtual machine. You'd set up a RAID or similar volume and all your VMs will be on that volume. A physical disk for each VM doesn't make much sense. What is an SSH slot?
    – essjae
    Commented Feb 9, 2021 at 17:29
  • sorry my bad I wrote SSH instead of SSD, twice!
    – lese
    Commented Feb 10, 2021 at 0:13
  • I really don't understand how could not impact performances if multiple guest write to the same disk at the same time
    – lese
    Commented Feb 10, 2021 at 0:19
  • @lese this depends entirely on whether the guest generates enough data throughput to saturate the connection capabilities of a hard drive and its connectors. One of the benefits of virtualization is different loads, with different peak and slack times, can peacefully exist on the same host without significantly impacting each others performance for this very reason.
    – music2myear
    Commented Feb 10, 2021 at 1:14
  • In choosing the appropriate hardware for your virtualized system you need to know your loads, their estimated throughput for give time periods, and then you'll be able to clear see whether what you've been told makes any sense or not.
    – music2myear
    Commented Feb 10, 2021 at 1:15

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