On Sat, Mar 31, 2018 at 11:09 PM, Ning Yao <zay11022@xxxxxxxxx> wrote:
> Thanks, it sounds like it is a good way to do the preparation of the
> device partition and LV in the orchestration tools.
Yes, I think this is the best path.
> So in this way, I think the logic of creating LV with lvm-cache also
> suitable to do by uses, not in ceph-volume, right? it seems also
> oversimplifying. And for simplicity, we just need to create LV with
> lvmcache and pass to ceph-volume.
As long as you can produce an LV, ceph-volume will work. We don't test
it currently, but we've tried it out with dmcache/lvmcache without
issues.
Now, ceph-ansible support for LV creation is planned, so that may help
you out if we fit your use cases.
> Regards
> Ning Yao
>
>
> 2018-03-31 20:48 GMT+08:00 Alfredo Deza <adeza@xxxxxxxxxx>:
>> On Sat, Mar 31, 2018 at 2:31 AM, Ning Yao <zay11022@xxxxxxxxx> wrote:
>>> Hi, Sage
>>>
>>> Although we have ceph-volume now, ceps-volume cannot work as expected
>>> in most of scenarios. For example:
>>>
>>> when we use:
>>>
>>> ceph-volume lvm prepare --filestore --data /dev/sda --journal /dev/sdl1 or
>>> ceph-volume lvm prepare --bluestore --data /dev/sda --block.db /dev/sdl1
>>>
>>> 1. we need to create a Physical Volume for /dev/sda before it can be
>>> used. and ceph-volume does not help us to do that
>>
>> Not sure what you mean by this. In that scenario, ceph-volume will use
>> /dev/sda and convert it to a single logical volume for "data". This is
>> even
>> how our tests work. If you are hitting errors, please give us some
>> examples on how to replicate.
>>
>>> 2. the params of --journal or --block.db must be a partitioned disk
>>> such as /dev/sdl1 or /dev/sdl1, and cannot be a raw device without
>>> partition -- /dev/sdl like ceps-disk does and automatically create the
>>> partition by using sgdisk.
>>
>> This is partially true. It can be a partition *or* a logical volume.
>> ceph-volume will not create partitions for a user because
>> this has been one of the most problematic pain points in ceph-disk.
>> Creating a partition is simple, but programmatically understanding
>> how to do partitions in any scenario that users throw at us is asking
>> to go back to ceph-disk issues.
>>
>> ceph-volume is currently tremendously robust and I am hesitant to add
>> this kind of helpfulness that has brought us issues before.
>>
>>> 3. we must explicitly use --journal or --block.db, --block.wal to tell
>>> ceph-volume where to put the data. It cannot be automatically
>>> partition or create multiple logical volumes for different usage, such
>>> as
>>> lvcreate --size 100M VG -n odd-block-meta-{uuid}
>>> lvcreate --size {bluestore_block_db_size} VG -n osd-block-db-{uuid}
>>> lvcreate --size {bluestore_block_wal_size} VG -n osd-block-wal-{uuid}
>>> lvcreate -l 100%FREE VG -n osd-block-{uuid} (use the left space for data)
>>>
>>
>> Again, this is oversimplifying. Creating an LV can be done in dozens
>> of ways, not just this one. The code to support this deployment
>> complexity
>> would not be a good return-over-investment.
>>
>> You can just specify the data device and ceph-volume will create a
>> full bluestore OSD for you, and yes, it will want to know what is your
>> wal or db device
>> if you want to use one.
>>
>>
>>> it seems now hard to switch to ceph-volume from ceps-disk. And if
>>> though, we need to do much extra work in ceph-ansible and help to
>>> prepare all the thing above. so is there any plan to enhance the
>>> function, or design spec of ceph-volume? and we may help on this.
>>
>> I would suggest investing in a configuration management system that
>> can help automate all the use cases you need. ceph-ansible can do a
>> bit of this already for you, and we are planning
>> on adding more support to help out creating LVs for a user.
>>
>> *However*, even on ceph-ansible, I am going to push towards a
>> simplistic approach, and not support all the various different ways
>> you can create a logical volume. This will no doubt leave
>> a lot of use cases out of luck, but it is a good way to provide
>> robustness on the tooling on the things we know will work right.
>>
>> If using ceph-ansible, it isn't hard to pre setup your machines with
>> the logical volume creation you have used as examples here.
>>>
>>>
>>> Regards
>>> Ning Yao
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