Re: null characters at the end of the file on hard reboot of VM

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Hello Kate,

thank you for your answer. Are you using ext4 or xfs in your VMs?

Kind regards,
Laszlo


On 08.04.2017 14:11, Kate Ward wrote:
I had a similar issue where files were padded out to the length of ceph.dir.layout.stripe_unit (see email entitled "Issue with Ceph padding files out to ceph.dir.layout.stripe_unit size" on this list). I never found a solution, but I can say that I am currently running 10.2.6 and haven't seen the issue so far reappear. 10.2.5 worked as well as best I recall.

I realise I'm running the next release after you, and that the circumstances aren't the same, but the patterns of behaviour are similar enough that I wanted to raise awareness.

k8

On Sat, Apr 8, 2017 at 6:39 AM Laszlo Budai <laszlo@xxxxxxxxxxxxxxxx <mailto:laszlo@xxxxxxxxxxxxxxxx>> wrote:

    Hello Peter,

    Thank you for your answer.
    In our setup we have the virtual machines running in KVM, and accessing the ceph storage using librbd.
    The rbd cache is set to "writethrough until flush = true". Here it is the result of ceph config show | grep cache :
    # ceph --admin-daemon /run/ceph/guests/ceph-client.cinder.30601.140275026217152.asok config show | grep cache
         "debug_objectcacher": "0\/5",
         "mon_osd_cache_size": "10",
         "mon_cache_target_full_warn_ratio": "0.66",
         "mon_warn_on_cache_pools_without_hit_sets": "true",
         "client_cache_size": "16384",
         "client_cache_mid": "0.75",
         "mds_cache_size": "100000",
         "mds_cache_mid": "0.7",
         "mds_dump_cache_on_map": "false",
         "mds_dump_cache_after_rejoin": "false",
         "osd_pool_default_cache_target_dirty_ratio": "0.4",
         "osd_pool_default_cache_target_full_ratio": "0.8",
         "osd_pool_default_cache_min_flush_age": "0",
         "osd_pool_default_cache_min_evict_age": "0",
         "osd_tier_default_cache_mode": "writeback",
         "osd_tier_default_cache_hit_set_count": "4",
         "osd_tier_default_cache_hit_set_period": "1200",
         "osd_tier_default_cache_hit_set_type": "bloom",
         "osd_tier_default_cache_min_read_recency_for_promote": "1",
         "osd_map_cache_size": "500",
         "osd_pg_object_context_cache_count": "64",
         "leveldb_cache_size": "134217728",
         "rocksdb_cache_size": "0",
         "filestore_omap_header_cache_size": "1024",
         "filestore_fd_cache_size": "128",
         "filestore_fd_cache_shards": "16",
         "keyvaluestore_header_cache_size": "4096",
         "rbd_cache": "true",
         "rbd_cache_writethrough_until_flush": "true",
         "rbd_cache_size": "134217728",
         "rbd_cache_max_dirty": "100663296",
         "rbd_cache_target_dirty": "67108864",
         "rbd_cache_max_dirty_age": "1",
         "rbd_cache_max_dirty_object": "0",
         "rbd_cache_block_writes_upfront": "false",
         "rgw_cache_enabled": "true",
         "rgw_cache_lru_size": "10000",
         "rgw_keystone_token_cache_size": "10000",
         "rgw_bucket_quota_cache_size": "10000",


    I did some tests and the problem has appeared when I was using ext4 in the VM, but not in the case of xfs.
    I did an other test when I was calling a sync at the end of the while loop, and in this case the issue did NOT appeared.


    Kind regards,
    Laszlo

    On 08.04.2017 00:07, Peter Maloney wrote:
    > You should describe your configuration...
    >
    > krbd? librbd? cephfs?
    > is rbd_cache = true?
    > rbd cache writethrough until flush = true?
    > is it kvm?
    > maybe the filesystem in the VM is relevant
    >
    > (I saw something similar testing cephfs... if I blacklisted a client and
    > then force unmounted, I would get whole files (appended I think) or ends
    > of files (new files) with zeros)
    >
    > On 04/07/17 13:36, Laszlo Budai wrote:
    >> Hello,
    >>
    >> we have observed that there are null characters written into the open
    >> files when hard rebooting a VM. Is tis a known issue?
    >> Our VM is using ceph (0.94.10) storage.
    >> we have a script like this:
    >> while sleep 1; do date >> somefile ; done
    >>
    >> if we hard reset the VM while the above line is running we end up with
    >> NULL characters in the file :
    >>
    >> 00000000  54 68 75 20 41 70 72 20  20 36 20 31 34 3a 33 37  |Thu Apr
    >> 6 14:37|
    >> 00000010  3a 33 33 20 43 45 53 54  20 32 30 31 37 0a 54 68  |:33 CEST
    >> 2017.Th|
    >> 00000020  75 20 41 70 72 20 20 36  20 31 34 3a 33 37 3a 33  |u Apr  6
    >> 14:37:3|
    >> 00000030  34 20 43 45 53 54 20 32  30 31 37 0a 54 68 75 20  |4 CEST
    >> 2017.Thu |
    >> 00000040  41 70 72 20 20 36 20 31  34 3a 33 37 3a 33 35 20  |Apr  6
    >> 14:37:35 |
    >> 00000050  43 45 53 54 20 32 30 31  37 0a 54 68 75 20 41 70  |CEST
    >> 2017.Thu Ap|
    >> 00000060  72 20 20 36 20 31 34 3a  33 37 3a 33 36 20 43 45  |r  6
    >> 14:37:36 CE|
    >> 00000070  53 54 20 32 30 31 37 0a  54 68 75 20 41 70 72 20  |ST
    >> 2017.Thu Apr |
    >> 00000080  20 36 20 31 34 3a 33 37  3a 33 39 20 43 45 53 54  | 6
    >> 14:37:39 CEST|
    >> 00000090  20 32 30 31 37 0a 54 68  75 20 41 70 72 20 20 36  | 2017.Thu
    >> Apr  6|
    >> 000000a0  20 31 34 3a 33 37 3a 34  30 20 43 45 53 54 20 32  | 14:37:40
    >> CEST 2|
    >> 000000b0  30 31 37 0a 54 68 75 20  41 70 72 20 20 36 20 31  |017.Thu
    >> Apr  6 1|
    >> 000000c0  34 3a 33 37 3a 34 31 20  43 45 53 54 20 32 30 31  |4:37:41
    >> CEST 201|
    >> 000000d0  37 0a 00 00 00 00 00 00  00 00 00 00 00 00 00 00
    >> |7...............|
    >> 000000e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
    >> |................|
    >>
    >> We've observed the same in the syslog file also.
    >>
    >> Any thoughts about it?
    >>
    >> kind regards,
    >> Laszlo
    >> _______________________________________________
    >> ceph-users mailing list
    >> ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx>
    >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
    >
    >
    >
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