Re: [pve-devel] [RFC qemu 1/1] block/rbd: add @keyring-file option to BlockdevOptionsRbd

["DERUMIER, Alexandre via pve-devel" <pve-devel@lists.proxmox.com>]

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From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.ebner@proxmox.com" <f.ebner@proxmox.com>
Subject: Re: [RFC qemu 1/1] block/rbd: add @keyring-file option to BlockdevOptionsRbd
Date: Mon, 12 May 2025 13:39:27 +0000
Message-ID: <330ddb6da2469b425acda6ceb9cdaf5a510a854f.camel@groupe-cyllene.com>


Am 12.05.25 um 12:57 schrieb DERUMIER, Alexandre:
> for blockdev, do we still use a ceph config file in /var/run for
> potential others rbd client options ?

>>Not currently, but we can add that later if we consider it worth it.
>>We
>>would need to merge with the storage's already existing ceph.conf and
>>not only write the new options. For now, users can adapt their
>>storage's
>>ceph.conf as desired.

they still are this rbd_cache_policy for efidisk to fix
https://bugzilla.proxmox.com/show_bug.cgi?id=3329


# SPI flash does lots of read-modify-write OPs, without writeback this
gets really slow #3329
      if ($path =~ m/^rbd:/) {
          $var_drive_str .= ',cache=writeback';
          $path .= ':rbd_cache_policy=writeback'; # avoid write-around,
we *need* to cache writes too
      }



I'm not sure, but maybe it's fixed in qemu , the biggest problem was
that every single byte write was push to the storage without any buffer
(so it was pretty slow with rbd crush).
but maybe it ok now with:
https://github.com/qemu/qemu/commit/284a7ee2e290e0c9b8cd3ea6164d92386933054f

(I don't have tested it)

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