problèmes de montage automatique

J'ai un Mac Mini sous Yosemite qui a des problèmes de performance. Lorsque l'on regarde l'activité du disque avec opensnoop J'ai remarqué que automount effectue des tonnes d'accès comme suit

  UID    PID COMM          FD PATH
    0   1124 automountd     4 /etc/auto_home
    0   1124 automountd     6 /etc/auto_home
    0  55536 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55536 od_user_homes   7 /usr/libexec
    0  55536 od_user_homes   7 /usr/libexec
    0  55536 od_user_homes   7 /usr/libexec/od_user_homes
    0   1124 automountd     4 /etc/auto_home
    0   1124 automountd     6 /etc/auto_home
    0   1124 automountd     6 /usr/libexec/od_user_homes
  501    464 syncdefaultsd   4 /Users/corti/Library/SyncedPreferences/.dat01d0.559
    0   1124 automountd     6 /usr/libexec/od_user_homes
    0     58 opendirectoryd   9 /var/db/dslocal/nodes//Default/users/corti.plist
    0  55537 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55537 od_user_homes   7 /usr/libexec
    0  55537 od_user_homes   7 /usr/libexec
    0  55537 od_user_homes   7 /usr/libexec/od_user_homes
    0     58 opendirectoryd   9 /var/db/dslocal/nodes//Default/users/corti.plist
    0  55538 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55538 od_user_homes   7 /usr/libexec
    0  55538 od_user_homes   7 /usr/libexec/od_user_homes
    0  55539 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55539 od_user_homes   7 /usr/libexec
    0  55539 od_user_homes   7 /usr/libexec
    0   1124 automountd     4 /etc/auto_home
    0   1124 automountd     6 /etc/auto_home
    0   1124 automountd     6 /usr/libexec/od_user_homes
    0  55540 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55540 od_user_homes   7 /usr/libexec
    0  55540 od_user_homes   7 /usr/libexec
    0   1124 automountd     4 /etc/auto_home
    0   1124 automountd     6 /etc/auto_home
    0   1124 automountd     6 /usr/libexec/od_user_homes
    0  55541 od_user_homes   5 /System/Library/OpenDirectory/request-schema.plist
    0  55541 od_user_homes   7 /usr/libexec
    0  55541 od_user_homes   7 /usr/libexec
    0  55541 od_user_homes   7 /usr/libexec/od_user_homes

Des centaines d'accès par seconde. Est-ce normal ? Quel est le problème ?