Re: [gentoo-user] Intel(R) C600 SAS Controller

[thegeezer <thegeezer@thegeezer.net>]

On 06/11/2014 11:34 AM, Stefan G. Weichinger wrote:
> Am 11.06.2014 12:14, schrieb thegeezer:
>
>>> Basically 3 RAID-6 hw-raids over 6 SAS hdds.
>> OK so i'm confused again.   RAID6 requires minimum of 4 drives.
>> if you have 3 raid6's then you would need 12 drives (coffee hasn't quite
>> activated in me yet so my maths may not be right)
>> or do you have essentially the first part of each of the six drives be
>> virtual disk 1, the second part of each of the six drives virtual disk 2
>> and the third part be virtual disk 3 -- if this is the case bear in mind
>> that the slowest part of the disk is the end of the disk -- so you are
>> essentially hobbling your virtual disk3 but only a little, instead of
>> being around 150MB/sec it might run at 80.
>
> I'd be happy to see 80 !
>
> Ran atop now while dd-ing stuff to an external disk and got ~1MB/s for
> 2.5GB of data.
>
> (this is even too slow for USB ...)
>
> I am unsure what to post here from atop ... ?
>
>
> To the initial question:
>
> Yes, imagine the six disks "split" or partitioned at the level of the
> hardware raid controller (as you described above).
>
>> you might also like to try a simple test of the following (yes lvs count
>> as block devices)
>> # hdparm -t /dev/sda
>> # hdparm -t /dev/sdb
>> # hdparm -t /dev/sdc
>> # hdparm -t /dev/vg01/winserver_disk0
>> # hdparm -t /dev/vg01/amhold
> everything around 380 MB/s ... only ~350 MB/s for
> /dev/vg01/winserver_disk0 (which still is nice)


OK here is the clue.
if the LVs are also showing such fast speed, then please can you show
your command that you are trying to run that is so slow ?