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

[Fabian Ebner <f.ebner@proxmox.com>]

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?

>>   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);
>>