gjournal+gstripe+gmirror question

[Alexei Troussov]

Hello All,

I decided to build multi-terabyte data storage (file server) using 4 x  
1Tb disks. No special raid controller is used, FreeBSD 7.1 is running  
on another disk, so the disk array is going to be used for file  
storage only.
So, I tried several combinations of gmirror/gstripe and put gjournal  
on it:

1) two mirrors and stripe on them
2) two stripes and mirror on them

Both configurations gave excellent I/O speed (around 100Mb/sec), and I  
chose the first one as it needs less time to resync disks when one of  
the mirrors fails. To make picture more complete, I didn't try graid3  
because it seems to load CPU more than configs above, which is not  
good for my barebone :)

Now when my top-level gstripe gets "gjournal"-ed, I see relatively  
poor write speed around 20-30 Mb/sec.
As far as I understand from man gjournal and some posts here,  
performance usually drops about 40-50%, but what I have is much worse...

Are there a better way to configure/tune the whole thing?
Thanks in advance!

PS Here is my current playground config:
--------
 > gmirror list
Geom name: gm0
State: COMPLETE
Components: 1
Balance: round-robin
Slice: 4096
Flags: NONE
GenID: 0
SyncID: 1
ID: 2111539126
Providers:
1. Name: mirror/gm0
    Mediasize: 1000204885504 (932G)
    Sectorsize: 512
    Mode: r1w1e2
Consumers:
1. Name: ad10
    Mediasize: 1000204886016 (932G)
    Sectorsize: 512
    Mode: r1w1e1
    State: ACTIVE
    Priority: 0
    Flags: NONE
    GenID: 0
    SyncID: 1
    ID: 3300348150
2. Name: ad12
    Mediasize: 1000204886016 (932G)
    Sectorsize: 512
    Mode: r1w1e1
    State: ACTIVE
    Priority: 0
    Flags: NONE
    GenID: 0
    SyncID: 1
    ID: 4291633068

Geom name: gm1
State: COMPLETE
Components: 2
Balance: round-robin
Slice: 4096
Flags: NONE
GenID: 0
SyncID: 1
ID: 835525163
Providers:
1. Name: mirror/gm1
    Mediasize: 1000204885504 (932G)
    Sectorsize: 512
    Mode: r1w1e2
Consumers:
1. Name: ad11
    Mediasize: 1000204886016 (932G)
    Sectorsize: 512
    Mode: r1w1e1
    State: ACTIVE
    Priority: 0
    Flags: NONE
    GenID: 0
    SyncID: 1
    ID: 1770536936
2. Name: ad13
    Mediasize: 1000204886016 (932G)
    Sectorsize: 512
    Mode: r1w1e1
    State: ACTIVE
    Priority: 0
    Flags: NONE
    GenID: 0
    SyncID: 1
    ID: 922042393

 > gstripe list
Geom name: gs0
State: UP
Status: Total=2, Online=2
Type: AUTOMATIC
Stripesize: 131072
ID: 1106325435
Providers:
1. Name: stripe/gs0
    Mediasize: 2000409591808 (1.8T)
    Sectorsize: 512
    Mode: r1w1e1
Consumers:
1. Name: mirror/gm0
    Mediasize: 1000204885504 (932G)
    Sectorsize: 512
    Mode: r1w1e2
    Number: 0
2. Name: mirror/gm1
    Mediasize: 1000204885504 (932G)
    Sectorsize: 512
    Mode: r1w1e2
    Number: 1
--------

Have a nice day,
Alex