Re: [pve-devel] [PATCH manager] fix #4631: ceph: osd: create: add osds-per-device

[Aaron Lauterer <a.lauterer@proxmox.com>]

responses inline

On 8/21/23 10:20, Fiona Ebner wrote:
> Am 18.04.23 um 14:26 schrieb Aaron Lauterer:
>> Allows to automatically create multiple OSDs per physical device. The
>> main use case are fast NVME drives that would be bottlenecked by a
>> single OSD service.
>>
>> By using the 'ceph-volume lvm batch' command instead of the 'ceph-volume
>> lvm create' for multiple OSDs / device, we don't have to deal with the
>> split of the drive ourselves.
>>
>> But this means that the parameters to specify a DB or WAL device won't
>> work as the 'batch' command doesn't use them. Dedicated DB and WAL
>> devices don't make much sense anyway if we place the OSDs on fast NVME
>> drives.
>>
>> Some other changes to how the command is built were needed as well, as
>> the 'batch' command needs the path to the disk as a positional argument,
>> not as '--data /dev/sdX'.
>> We drop the '--cluster-fsid' paramter because the 'batch' command
>> doesn't accept it. The 'create' will fall back to reading it from the
>> ceph.conf file.
>>
>> Removal of OSDs works as expected without any code changes. As long as
>> there are other OSDs on a disk, the VG & PV won't be removed, even if
>> 'cleanup' is enabled.
>>
>> Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
>> ---
> 
> I noticed a warning while testing
> 
> --> DEPRECATION NOTICE
> --> You are using the legacy automatic disk sorting behavior
> --> The Pacific release will change the default to --no-auto
> --> passed data devices: 1 physical, 0 LVM
> --> relative data size: 0.3333333333333333
> 
> Note that I'm on Quincy, so maybe they didn't still didn't change it :P

Also shows up when using `ceph-volume lvm batch …` directly. So I guess not much 
we can do about it after consulting the man page.
> 
>> @@ -275,6 +275,12 @@ __PACKAGE__->register_method ({
>>   		type => 'string',
>>   		description => "Set the device class of the OSD in crush."
>>   	    },
>> +	    'osds-per-device' => {
>> +		optional => 1,
>> +		type => 'number',
> 
> should be integer

will change
> 
>> +		minimum => '1',
>> +		description => 'OSD services per physical device. Can improve fast NVME utilization.',
> 
> Can we add an explicit recommendation against doing it for other disk
> types? I imagine it's not beneficial for those, or?

What about something like:
"Only useful for fast NVME devices to utilize their performance better."?

> 
>> +	    },
>>   	},
>>       },
>>       returns => { type => 'string' },
>> @@ -294,6 +300,15 @@ __PACKAGE__->register_method ({
>>   	# extract parameter info and fail if a device is set more than once
>>   	my $devs = {};
>>   
>> +	# allow 'osds-per-device' only without dedicated db and/or wal devs. We cannot specify them with
>> +	# 'ceph-volume lvm batch' and they don't make a lot of sense on fast NVMEs anyway.
>> +	if ($param->{'osds-per-device'}) {
>> +	    for my $type ( qw(db_dev wal_dev) ) {
>> +		die "Cannot use 'osds-per-device' parameter with '${type}'"
> 
> Missing newline after error message.
> Could also use raise_param_exc().

Ah thanks. Will switch it to an `raise_param_exc()` where we don't need the 
newline AFAICT?
> 
>> +		    if $param->{$type};
>> +	    }
>> +	}
>> +
>>   	my $ceph_conf = cfs_read_file('ceph.conf');
>>   
>>   	my $osd_network = $ceph_conf->{global}->{cluster_network};