Active directory 为什么我在objectGUID上的Active Directory LDAP查询速度慢？

我正在使用如下查询从AD检索所有用户：

(&(objectClass=user)(objectCategory=person))

而且它需要相当长的时间（5万用户需要8分钟）

我试图通过在objectGUID上添加一个条件，将其拆分为16个并行查询，如

(&(objectGUID>=\00)(objectGUID<=\10))
(&(objectGUID>=\10)(objectGUID<=\20))

（&（objectGUID>=\00）（objectGUID=\10）（objectGUID
(&(objectGUID>=\00)(objectGUID<=\10)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\30)(objectGUID<=\40)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\10)(objectGUID<=\20)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\20)(objectGUID<=\30)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\40)(objectGUID<=\50)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\50)(objectGUID<=\60)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\60)(objectGUID<=\70)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\70)(objectGUID<=\80)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\80)(objectGUID<=\90)): Starting fetch 03/13/2013 15:12:52
(&(objectGUID>=\90)(objectGUID<=\A0)): Starting fetch 03/13/2013 15:12:53
(&(objectGUID>=\A0)(objectGUID<=\B0)): Starting fetch 03/13/2013 15:12:54
(&(objectGUID>=\B0)(objectGUID<=\C0)): Starting fetch 03/13/2013 15:12:55
(&(objectGUID>=\C0)(objectGUID<=\D0)): Starting fetch 03/13/2013 15:12:56
(&(objectGUID>=\D0)(objectGUID<=\E0)): Starting fetch 03/13/2013 15:12:57
(&(objectGUID>=\E0)(objectGUID<=\F0)): Starting fetch 03/13/2013 15:12:58
(objectGUID>=\F0): Starting fetch 03/13/2013 15:12:59
(&(objectGUID>=\00)(objectGUID<=\10)): Ended fetch 03/13/2013 15:13:25, 3327 results
(&(objectGUID>=\20)(objectGUID<=\30)): Ended fetch 03/13/2013 15:14:00, 3225 results
(&(objectGUID>=\40)(objectGUID<=\50)): Ended fetch 03/13/2013 15:14:29, 3209 results
(&(objectGUID>=\50)(objectGUID<=\60)): Ended fetch 03/13/2013 15:14:58, 3133 results
(&(objectGUID>=\30)(objectGUID<=\40)): Ended fetch 03/13/2013 15:15:25, 3179 results
(&(objectGUID>=\70)(objectGUID<=\80)): Ended fetch 03/13/2013 15:15:56, 3291 results
(&(objectGUID>=\10)(objectGUID<=\20)): Ended fetch 03/13/2013 15:16:24, 3200 results
(&(objectGUID>=\60)(objectGUID<=\70)): Ended fetch 03/13/2013 15:16:57, 3222 results
(&(objectGUID>=\80)(objectGUID<=\90)): Ended fetch 03/13/2013 15:17:26, 3227 results
(&(objectGUID>=\90)(objectGUID<=\A0)): Ended fetch 03/13/2013 15:17:54, 3084 results
(&(objectGUID>=\A0)(objectGUID<=\B0)): Ended fetch 03/13/2013 15:18:30, 3195 results
(&(objectGUID>=\B0)(objectGUID<=\C0)): Ended fetch 03/13/2013 15:19:06, 3208 results
(&(objectGUID>=\C0)(objectGUID<=\D0)): Ended fetch 03/13/2013 15:19:35, 3084 results
(&(objectGUID>=\D0)(objectGUID<=\E0)): Ended fetch 03/13/2013 15:20:04, 3181 results
(&(objectGUID>=\E0)(objectGUID<=\F0)): Ended fetch 03/13/2013 15:20:36, 3149 results
(objectGUID>=\F0): Ended fetch 03/13/2013 15:21:05, 3200 results