Re: [pve-devel] [PATCH qemu-server] fix #3324: clone disk: use larger blocksize for EFI disk when possible

[Stefan Reiter <s.reiter@proxmox.com>]

On 3/1/21 11:06 AM, Fabian Ebner wrote:
> Am 01.03.21 um 10:54 schrieb Stefan Reiter:
>> On 3/1/21 10:42 AM, Fabian Ebner wrote:
>>> Moving to Ceph is very slow when bs=1. Instead, use the biggest 
>>> possible power
>>> of two <= 1024. At the moment our EFI image sizes are multiples of 
>>> 1024, so
>>> just using 1024 wouldn't be a problem, but this feels more future-proof.
>>>
>>> Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
>>> ---
>>>
>>> I did not see an way for 'qemu-img dd' to use a larger blocksize 
>>> while still
>>> specifying the exact total size if it is not a multiple of the 
>>> blocksize.
>>>
>>
>> Could it make sense to just set the block size equal to the image size 
>> with count=1 ? Since the images will always be very small anyway...
>>
> 
> Note that AAVMF_VARS.fd is 64 MiB. Are blocksizes that big a good idea?
> 

That'd be too much, but the VARS file shouldn't be copied anyway? Only 
the efidisk attached to the VM?

>>>   PVE/QemuServer.pm | 10 +++++++++-
>>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
>>> index f401baf..e579cdf 100644
>>> --- a/PVE/QemuServer.pm
>>> +++ b/PVE/QemuServer.pm
>>> @@ -6991,7 +6991,15 @@ sub clone_disk {
>>>           # that is given by the OVMF_VARS.fd
>>>           my $src_path = PVE::Storage::path($storecfg, $drive->{file});
>>>           my $dst_path = PVE::Storage::path($storecfg, $newvolid);
>>> -        run_command(['qemu-img', 'dd', '-n', '-O', $dst_format, 
>>> "bs=1", "count=$size",
>>> +
>>> +        # Ceph doesn't like too small blocksize, see bug #3324
>>> +        my $bs = 1;
>>> +        while ($bs < $size && $bs < 1024 && $size % $bs == 0) {
>>> +            $bs *= 2;
>>> +        }
>>> +        my $count = $size / $bs;
>>> +
>>> +        run_command(['qemu-img', 'dd', '-n', '-O', $dst_format, 
>>> "bs=$bs", "count=$count",
>>>               "if=$src_path", "of=$dst_path"]);
>>>           } else {
>>>           qemu_img_convert($drive->{file}, $newvolid, $size, 
>>> $snapname, $sparseinit);
>>>