[DRBD-user] drbd tranfer limitations (random and sequential acccess) using raw

[crsurf]

Hello list
I´m using drbd in a Gigabit network (crossover cable) and when I synchronize data (sequential read/write) the tranfer hit to 30~40 Mb/s, but when I make inserts into database (random read/write) that access drbd device via raw, the transfer rate hit only 5~6 Mb/s. Exists some way to improve this performance?
I increased the sndbuf-size to 256K, but no such effect. I increase interface MTU to 9000 and no such effect too.
One database process that run in 4 min. without replication, run in 30 min. with replication.
Now I´m trying using filesystem jfs instead raw to view if the performance will be improved.
Maybe sync-nice can help us?
There is my drbd.conf 
 [root at SRVSYB02 nagios]# cat /etc/drbd.conf
# Sybase Master
       resource drbd0 {
         protocol=C
         fsckcmd=/bin/true
         #skip-wait
         load-only
         inittimeout=30
         disk {
           do-panic
           disk-size = 63461
         }
         net {
           skip-sync
           sync-min    = 599999
           sync-max    = 600000 # maximal average syncer bandwidth
           tl-size     = 5000   # transfer log size, ensures strict write ordering
           timeout     = 60     # 0.1 seconds
           connect-int = 10     # seconds
           ping-int    = 10     # seconds
           sndbuf-size = 262144 #
         }
         on SRVSYB01 {
           device=/dev/nb0
           disk=/dev/vg01/syb.master
           address=172.22.2.4
           port=7789
         }
         on SRVSYB02 {
           device=/dev/nb0
           disk=/dev/vg01/syb.master
           address=172.22.2.5
           port=7789
         }
       }
# Sybase Sybsystemprocs
       resource drbd1 {
         protocol=C
         fsckcmd=/bin/true
         #skip-wait
         load-only
         inittimeout=30
         disk {
           do-panic
           disk-size = 206269
         }
         net {
           skip-sync
           sync-min    = 599999
           sync-max    = 600000 # maximal average syncer bandwidth
           tl-size     = 5000   # transfer log size, ensures strict write ordering
           timeout     = 60     # 0.1 seconds
           connect-int = 10     # seconds
           ping-int    = 10     # seconds
           sndbuf-size = 262144 #
         }
         on SRVSYB01 {
           device=/dev/nb1
           disk=/dev/vg01/syb.sybprocs
           address=172.22.2.4
           port=7790
         }
         on SRVSYB02 {
           device=/dev/nb1
           disk=/dev/vg01/syb.sybprocs
           address=172.22.2.5
           port=7790
         }
       }
# Sybase Banco01
       resource drbd2 {
         protocol=C
         fsckcmd=/bin/true
         #skip-wait
         load-only
         inittimeout=30
         disk {
           do-panic
           disk-size = 33555244
         }
         net {
           skip-sync
           sync-min    = 599999
           sync-max    = 600000 # maximal average syncer bandwidth
           tl-size     = 5000   # transfer log size, ensures strict write ordering
           timeout     = 60     # 0.1 seconds
           connect-int = 10     # seconds
           ping-int    = 10     # seconds
           sndbuf-size = 262144 #
         }
         on SRVSYB01 {
           device=/dev/nb2
           disk=/dev/vg01/syb.bco01
           address=172.22.2.4
           port=7791
         }
         on SRVSYB02 {
           device=/dev/nb2
           disk=/dev/vg01/syb.bco01
           address=172.22.2.5
           port=7791
         }
       }
# Sybase Log01
       resource drbd3 {
         protocol=C
         fsckcmd=/bin/true
         #skip-wait
         load-only
         inittimeout=30
         disk {
           do-panic
           disk-size = 8389856
         }
         net {
           skip-sync
           sync-min    = 599999
           sync-max    = 600000 # maximal average syncer bandwidth
           tl-size     = 5000   # transfer log size, ensures strict write ordering
           timeout     = 60     # 0.1 seconds
           connect-int = 10     # seconds
           ping-int    = 10     # seconds
           sndbuf-size = 262144 #
         }
         on SRVSYB01 {
           device=/dev/nb3
           disk=/dev/vg01/syb.log01
           address=172.22.2.4
           port=7792
         }
         on SRVSYB02 {
           device=/dev/nb3
           disk=/dev/vg01/syb.log01
           address=172.22.2.5
           port=7792
         }
       }

Grateful
Cristiano da Costa
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