It should be as expected. The reason is FileJournal will prepend
header and append footer to the transaction data, and if using
aio+dio, we need to align these. So normally for 4k io, it will become
5-6k filejournal write IIRC. Plus filestore writeback to filesystem,
it should be 2.5x. But local file system and disk should has some
merge tricky, it should be less than 2.5x.
On Sat, Feb 27, 2016 at 1:46 AM, James (Fei) Liu-SSI
<james.liu@xxxxxxxxxxxxxxx> wrote:
> Hi Cepher,
> We recently have tested the Ceph space amplification with filestore through writing data to ramdisk with rados bench. However, we found only
> 3584 MB was written from rados bench but totally 8658M(1G of total 9G of ramdisk was used for journal) was used in the ramdisk.
>
> The totally space amplification is 7658/3584 = 2.14. (It is surprising huge factor)
> 1. Cluster configuration:
> . One OSD and one MON are in the same machine with rados bench. Replication factor was set as 1.
> . ceph version from ceph master 5979c8e34fa2f3d7efa28c29fb90758b3f9f818 (45979c8e34fa2f3d7efa28c29fb90758b3f9f818)
> 2. Rados command we have been used :
> rados bench -p rbd -b 4096 --max-objects 1048576 300 write --no-cleanup
> 3. ceph cluster configuration:
> Please see appendix 1.
> 4. Results investigation.
> Please see appendix 0.
>
> Could anyone help to explain why the space amplification with filestore is huge? Thanks a lot.
>
> Regards,
> James
>
> Appendix 0:
>
> ssd@OptiPlex-9020-1:~/src/bluestore$ ceph df
> GLOBAL:
> SIZE AVAIL RAW USED %RAW USED
> 9206M 547M 8658M 94.05
> POOLS:
> NAME ID USED %USED MAX AVAIL OBJECTS
> rbd 0 3584M 38.93 547M 917505
> ssd@OptiPlex-9020-1:~/src/bluestore$ ceph -s
> cluster a7f64266-0894-4f1e-a635-d0aeaca0e993
> health HEALTH_WARN
> 1 near full osd(s)
> monmap e1: 1 mons at {localhost=127.0.0.1:6789/0}
> election epoch 3, quorum 0 localhost
> osdmap e7: 1 osds: 1 up, 1 in
> flags sortbitwise
> pgmap v31: 64 pgs, 1 pools, 3584 MB data, 896 kobjects
> 8658 MB used, 547 MB / 9206 MB avail
> 64 active+clean
> ssd@OptiPlex-9020-1:~/src/bluestore$ df -h
> Filesystem Size Used Avail Use% Mounted on
> /dev/sda2 2.7T 1.4T 1.2T 55% /
> none 4.0K 0 4.0K 0% /sys/fs/cgroup
> udev 5.9G 4.0K 5.9G 1% /dev
> tmpfs 1.2G 720K 1.2G 1% /run
> none 5.0M 0 5.0M 0% /run/lock
> none 5.9G 81M 5.8G 2% /run/shm
> none 100M 20K 100M 1% /run/user
> /dev/ram1 9.0G 8.4G 618M 94% /home/ssd/src/bluestore/ceph-deploy/osd/myosddata
>
> Journal size:
>
> -rw-r--r-- 1 ssd ssd 37 Feb 25 15:53 ceph_fsid
> drwxr-xr-x 132 ssd ssd 4096 Feb 25 15:53 current
> -rw-r--r-- 1 ssd ssd 37 Feb 25 15:53 fsid
> -rw-r--r-- 1 ssd ssd 21 Feb 25 15:53 magic
> -rw-r--r-- 1 ssd ssd 1073741824 Feb 25 15:53 myosdjournal
> -rw-r--r-- 1 ssd ssd 6 Feb 25 15:53 ready
> -rw-r--r-- 1 ssd ssd 4 Feb 25 15:53 store_version
> -rw-r--r-- 1 ssd ssd 53 Feb 25 15:53 superblock
> -rw-r--r-- 1 ssd ssd 10 Feb 25 15:53 type
> -rw-r--r-- 1 ssd ssd 2 Feb 25 15:53 whoami
>
> du -sh
> It shows current use 8G.
>
> Appendix 1:
> [global]
> fsid = a7f64266-0894-4f1e-a635-d0aeaca0e993
> auth_cluster_required = none
> auth_service_required = none
> auth_client_required = none
> filestore_xattr_use_omap = true
> filestore_max_sync_interval=10
> filestore_fd_cache_size = 64
> filestore_fd_cache_shards = 32
> filestore_op_threads = 6
> filestore_queue_max_ops=5000
> filestore_queue_committing_max_ops=5000
> journal_max_write_entries=1000
> journal_queue_max_ops=3000
> filestore_wbthrottle_enable=false
> filestore_queue_max_bytes=1048576000
> filestore_queue_committing_max_bytes=1048576000
> journal_max_write_bytes=1048576000
> journal_queue_max_bytes=1048576000
>
> osd_journal_size = 1024
> debug_lockdep = 0/0
> debug_context = 0/0
> debug_crush = 0/0
> debug_buffer = 0/0
> debug_timer = 0/0
> debug_filer = 0/0
> debug_objecter = 0/0
> debug_rados = 0/0
> debug_rbd = 0/0
> debug_journaler = 0/0
> debug_objectcatcher = 0/0
> debug_client = 0/0
> debug_osd = 0/0
> debug_optracker = 0/0
> debug_objclass = 0/0
> debug_filestore = 0/0
> debug_journal = 0/0
> debug_ms = 0/0
> debug_monc = 0/0
> debug_tp = 0/0
> debug_auth = 0/0
> debug_finisher = 0/0
> debug_heartbeatmap = 0/0
> debug_perfcounter = 0/0
> debug_asok = 0/0
> debug_throttle = 0/0
> debug_mon = 0/0
> debug_paxos = 0/0
> debug_rgw = 0/0
> debug_newstore = 0/0
> debug_keyvaluestore = 0/0
> osd_tracing = true
> osd_objectstore_tracing = true
> rados_tracing = true
> rbd_tracing = true
> osd_mount_options_xfs = rw,noatime,inode64,logbsize=256k,delaylog
> osd_mkfs_options_xfs = -f -i size=2048
> osd_op_threads = 32
> objecter_inflight_ops=102400
> ms_dispatch_throttle_bytes=1048576000
> objecter_infilght_op_bytes=1048576000
> osd_mkfs_type = xfs
> osd_client_message_size_cap = 0
> osd_client_message_cap = 0
> osd_enable_op_tracker = false
> mon_initial_members = localhost
> mon_host = 127.0.0.1
> mon data = '$CEPH_DEPLOY'/mon/mymondata
> mon cluster log file = '$CEPH_DEPLOY'/mon/mon.log
> keyring='$CEPH_DEPLOY'/ceph.client.admin.keyring
> run dir = '$CEPH_DEPLOY'/run
> [osd.0]
> osd data = '$CEPH_DEPLOY'/osd/myosddata
> osd journal = '$CEPH_DEPLOY'/osd/myosddata/myosdjournal
> #osd journal = '$WORKSPACE'/myosdjournal/myosdjournal
> log file = '$CEPH_DEPLOY'/osd/osd.log'
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