I looked at this system this morning, and the it actually finished what it was
doing. The erasure coded pool still contains all the data and the cache
pool has about a million zero sized objects:
GLOBAL:
SIZE AVAIL RAW USED %RAW USED OBJECTS
15090G 9001G 6080G 40.29 2127k
POOLS:
NAME ID CATEGORY USED %USED MAX AVAIL
OBJECTS DIRTY READ WRITE
cache-data 21 - 0 0 7962G
1162258 1057k 22969 3220k
cephfs-data 22 - 3964G 26.27 5308G
1014840 991k 891k 1143k
Definitely seems like a bug since I removed all references to these from the
filesystem
which created them.
I originally wrote 4.5 Tbytes of data into the file system, the erasure coded
pool is setup as 4+2, and the cache has a size limit of 1 Tbyte. Looks like not
all the data made it out of the cache tier before I removed content, it removed
the
content which was only present in the cache tier and created a zero sized object
in the cache for all the content. The used capacity is somewhat consistent with
this.
I tried to look at the extended attributes on one of the zero size object with
ceph-dencoder,
but it failed:
error: buffer::malformed_input: void
object_info_t::decode(ceph::buffer::list::iterator&) unknown encoding version >
15
Same error on one of the objects in the erasure coded pool.
Looks like I am a little too bleeding edge for this, or the contents of the
.ceph_ attribute are not an object_info_t
Steve
> On Feb 4, 2016, at 7:10 PM, Gregory Farnum <gfar...@redhat.com> wrote:
>
> On Thu, Feb 4, 2016 at 5:07 PM, Stephen Lord <steve.l...@quantum.com> wrote:
>>
>>> On Feb 4, 2016, at 6:51 PM, Gregory Farnum <gfar...@redhat.com> wrote:
>>>
>>> I presume we're doing reads in order to gather some object metadata
>>> from the cephfs-data pool; and the (small) newly-created objects in
>>> cache-data are definitely whiteout objects indicating the object no
>>> longer exists logically.
>>>
>>> What kinds of reads are you actually seeing? Does it appear to be
>>> transferring data, or merely doing a bunch of seeks? I thought we were
>>> trying to avoid doing reads-to-delete, but perhaps the way we're
>>> handling snapshots or something is invoking behavior that isn't
>>> amicable to a full-FS delete.
>>>
>>> I presume you're trying to characterize the system's behavior, but of
>>> course if you just want to empty it out entirely you're better off
>>> deleting the pools and the CephFS instance entirely and then starting
>>> it over again from scratch.
>>> -Greg
>>
>> I believe it is reading all the data, just from the volume of traffic and
>> the cpu load on the OSDs maybe suggests it is doing more than
>> just that.
>>
>> iostat is showing a lot of data moving, I am seeing about the same volume
>> of read and write activity here. Because the OSDs underneath both pools
>> are the same ones, I know that’s not exactly optimal, it is hard to tell what
>> which pool is responsible for which I/O. Large reads and small writes suggest
>> it is reading up all the data from the objects, the write traffic is I
>> presume all
>> journal activity relating to deleting objects and creating the empty ones.
>>
>> The 9:1 ratio between things being deleted and created seems odd though.
>>
>> A previous version of this exercise with just a regular replicated data pool
>> did not read anything, just a lot of write activity and eventually the
>> content
>> disappeared. So definitely related to the pool configuration here and
>> probably
>> not to the filesystem layer.
>
> Sam, does this make any sense to you in terms of how RADOS handles deletes?
> -Greg
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