really the chunksizes of two raid is different in this test，but I use same chunksize in two raid already, the result is the same.
the question is why write performance of  each single raid5 can reached to 1GB/s(dd),dd write two raid5 can only reach to 1.4GB/s，
Theoretically total performance can reached to 2GB/s，loss 30% .
is any contention in soft raid5?


------------------------------------------------------------------
发件人：Tommy Apel [off-list ref]
发送时间：2013年12月16日(星期一) 22:02
收件人：lilofile [off-list ref]
抄　送：linux-raid [off-list ref]
主　题：Re: 答复：答复：two raid5 performance

First off you chunksizes are different on the two volumes and secondly
if you're looking for throughput performance move them up to like 512K
or maybe more

2013/12/16 lilofile [off-list ref]:

the result of mdadm -D is as follows:

root@host0:~# mdadm  -D /dev/md126
/dev/md126:
        Version : 1.2
  Creation Time : Sat Dec  7 16:26:04 2013
     Raid Level : raid5
     Array Size : 1171499840 (1117.23 GiB 1199.62 GB)
  Used Dev Size : 234299968 (223.45 GiB 239.92 GB)
   Raid Devices : 6
  Total Devices : 6
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Fri Dec 13 22:51:04 2013
          State : active
 Active Devices : 6
Working Devices : 6
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : host0:md126
           UUID : aaa3075d:f25e3bd0:9dd347c5:fb58192f
         Events : 158

    Number   Major   Minor   RaidDevice State
       0      65      112        0      active sync   /dev/sdx
       1      65       96        1      active sync   /dev/sdw
       2      65       80        2      active sync   /dev/sdv
       3      65       64        3      active sync   /dev/sdu
       4      65       48        4      active sync   /dev/sdt
       6      65       32        5      active sync   /dev/sds
root@host0:~#


root@host0:~# mdadm  -D /dev/md129
/dev/md129:
        Version : 1.2
  Creation Time : Sun Dec  8 15:59:11 2013
     Raid Level : raid5
     Array Size : 1171498880 (1117.23 GiB 1199.61 GB)
  Used Dev Size : 234299776 (223.45 GiB 239.92 GB)
   Raid Devices : 6
  Total Devices : 6
    Persistence : Superblock is persistent

    Update Time : Mon Dec 16 21:50:45 2013
          State : clean
 Active Devices : 6
Working Devices : 6
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 128K

           Name : host0:md129  (local to host sc0)
           UUID : b80616a9:49540979:90b20aa6:1b22f67b
         Events : 31

    Number   Major   Minor   RaidDevice State
       0      65       16        0      active sync   /dev/sdr
       1      65        0        1      active sync   /dev/sdq
       2       8      224        2      active sync   /dev/sdo
       3       8      240        3      active sync   /dev/sdp
       4       8      208        4      active sync   /dev/sdn
       5       8      192        5      active sync   /dev/sdm
root@host0:~#


------------------------------------------------------------------
发件人：Tommy Apel [off-list ref]
发送时间：2013年12月16日(星期一) 21:32
收件人：lilofile [off-list ref]
抄　送：linux-raid [off-list ref]
主　题：Re: 答复：two raid5 performance

Please give us the output of mdadm -D for each array aswell, and just
in case, also the model of the SSD's in use

2013/12/16 Dag Nygren [off-list ref]:

quoted

On Monday 16 December 2013 15:57:42 lilofile wrote:

quoted

the disks involved in the array is sTEC ssd disk,they are connected by mpt2sas 6Gb/s

I/O bus to the card?

Best
Dag

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/Tommy

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