[ceph-users] CephFS - large omap object

Dylan McCulloch dmc at unimelb.edu.au
Mon Mar 18 05:14:52 PDT 2019


>> >> >cephfs does not create/use object "4.00000000".  Please show us some
>> >> >of its keys.
>> >> >
>> >>
>> >> https://pastebin.com/WLfLTgni
>> >> Thanks
>> >>
>> > Is the object recently modified?
>> >
>> >rados -p hpcfs_metadata stat 4.00000000
>> >
>>
>> $ rados -p hpcfs_metadata stat 4.00000000
>> hpcfs_metadata/4.00000000 mtime 2018-09-17 08:11:50.000000, size 0
>>
>please check if 4.00000000 has omap header and xattrs
>
>rados -p hpcfs_data listxattr 4.00000000
>
>rados -p hpcfs_data getomapheader 4.00000000
>

Not sure if that was a typo^^ and you would like the above commands run on the 4.00000000 object in the metadata pool.
Ran commands on both

$ rados -p hpcfs_data listxattr 4.00000000
error getting xattr set hpcfs_data/4.00000000: (2) No such file or directory
$ rados -p hpcfs_data getomapheader 4.00000000
error getting omap header hpcfs_data/4.00000000: (2) No such file or directory

$ rados -p hpcfs_metadata listxattr 4.00000000
layout
parent
$ rados -p hpcfs_metadata getomapheader 4.00000000
header (274 bytes) :
00000000  04 03 0c 01 00 00 01 00  00 00 00 00 00 00 00 00  |................|
00000010  00 00 00 00 00 00 03 02  28 00 00 00 00 00 00 00  |........(.......|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 01 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  00 00 00 00 03 02 28 00  00 00 00 00 00 00 00 00  |......(.........|
00000050  00 00 00 00 00 00 00 00  00 00 01 00 00 00 00 00  |................|
00000060  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000070  00 00 03 02 38 00 00 00  00 00 00 00 00 00 00 00  |....8...........|
00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000000b0  03 02 38 00 00 00 00 00  00 00 00 00 00 00 00 00  |..8.............|
000000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000000e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 01 00  |................|
000000f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000110  00 00                                             |..|
00000112

$ rados -p hpcfs_metadata getxattr 4.00000000 layout
????????
$ rados -p hpcfs_metadata getxattr 4.00000000 parent
<
lost+found

>> >> >On Mon, Mar 18, 2019 at 4:16 PM Dylan McCulloch <dmc at unimelb.edu.au> wrote:
>> >> >>
>> >> >> Hi all,
>> >> >>
>> >> >> We have a large omap object warning on one of our Ceph clusters.
>> >> >> The only reports I've seen regarding the "large omap objects" warning from other users were related to RGW bucket sharding, however we do not have RGW configured on this cluster.
>> >> >> The large omap object ~10GB resides in a CephFS metadata pool.
>> >> >>
>> >> >> It's perhaps worth mentioning that we had to perform disaster recovery steps [1] on this cluster last year after a network issue, so we're not sure whether this large omap object is a result of those previous recovery processes or whether it's completely unrelated.
>> >> >>
>> >> >> Ceph version: 12.2.8
>> >> >> osd_objectstore: Bluestore
>> >> >> RHEL 7.5
>> >> >> Kernel: 4.4.135-1.el7.elrepo.x86_64
>> >> >>
>> >> >> We have set: "mds_bal_fragment_size_max": "500000" (Default 100000)
>> >> >>
>> >> >> $ ceph health detail
>> >> >> HEALTH_WARN 1 large omap objects
>> >> >> LARGE_OMAP_OBJECTS 1 large omap objects
>> >> >>     1 large objects found in pool 'hpcfs_metadata'
>> >> >>     Search the cluster log for 'Large omap object found' for more details.
>> >> >>
>> >> >> # Find pg with large omap object
>> >> >> $ for i in `ceph pg ls-by-pool hpcfs_metadata | tail -n +2 | awk '{print $1}'`; do echo -n "$i: "; ceph pg $i query |grep num_large_omap_objects | head -1 | awk '{print $2}'; done | grep ": 1"
>> >> >> 20.103: 1
>> >> >>
>> >> >> # OSD log entry showing relevant object
>> >> >> osd.143 osd.143 172.26.74.23:6826/3428317 1380 : cluster [WRN] Large omap object found. Object: 20:c0ce80d4:::4.00000000:head Key count: 24698995 Size (bytes): 11410935690
>> >> >>
>> >> >> # Confirm default warning thresholds for large omap object
>> >> >> $ ceph daemon osd.143 config show | grep osd_deep_scrub_large_omap
>> >> >>     "osd_deep_scrub_large_omap_object_key_threshold": "2000000",
>> >> >>     "osd_deep_scrub_large_omap_object_value_sum_threshold": "1073741824",
>> >> >>
>> >> >> # Dump keys/values of problematic object, creates 46.65GB file
>> >> >> $ rados -p hpcfs_metadata listomapvals '4.00000000' > /tmp/hpcfs_metadata_object_omap_vals_4.00000000_20190304
>> >> >> $ ll /tmp/hpcfs_metadata_object_omap_vals_4.00000000_20190304
>> >> >> -rw-r--r-- 1 root root 50089561860 Mar  4 18:16 /tmp/hpcfs_metadata_object_omap_vals_4.00000000_20190304
>> >> >>
>> >> >> # Confirm key count matches OSD log entry warning
>> >> >> $ rados -p hpcfs_metadata listomapkeys '4.00000000' | wc -l
>> >> >> 24698995
>> >> >>
>> >> >> # The omap keys/vals for that object appear to have been unchanged/static for at least a couple of months:
>> >> >> $ sha1sum /tmp/hpcfs_metadata_object_omap_vals_4.00000000_20190304
>> >> >> fd00ceb68607b477626178b2d81fefb926460107  /tmp/hpcfs_metadata_object_omap_vals_4.00000000_20190304
>> >> >> $ sha1sum /tmp/hpcfs_metadata_object_omap_vals_4_00000000_20190108
>> >> >> fd00ceb68607b477626178b2d81fefb926460107  /tmp/hpcfs_metadata_object_omap_vals_4_00000000_20190108
>> >> >>
>> >> >> I haven't gone through all 24698995 keys yet, but while most appear to relate to objects in the hpcfs_data CephFS data pool, there are a significant number of keys (rough guess 25%) that don't appear to have corresponding objects in the hpcfs_data pool.
>> >> >>
>> >> >> Any assistance or pointers to troubleshoot further would be very much appreciated.
>> >> >>
>> >> >> Thanks,
>> >> >> Dylan
>> >> >>
>> >> >> [1] http://docs.ceph.com/docs/luminous/cephfs/disaster-recovery/
>> >> >>
>> >> >> _______________________________________________
>> >> >> ceph-users mailing list
>> >> >> ceph-users at lists.ceph.com
>> >> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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