[CentOS] Performance Issues

[Alain Spineux]

And what about a
raw disk tape to raw tape copy ?

# dd if=/dev/sda of=/dev/nst0 bs=32k count=32768

PS: 14 disk in raid 0 is very fragile, this should be used only for
caching data. With a PV220 maybe a backup engine then !

On 9/2/07, Dan Dansereau <ddansereau at hydropoint.com> wrote:
> My apology for cross posting
>
> We have a DELL6850 with 8Gbytes of memory,  four 3.2Ghz CPU's , perc 4
> raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault
> 220s, And a powervault 124T  LTO-3 tape systems on a separate
> 160Mbyte/sec adaptec SCSI card.
> The disks are configured as two 2Tbyte raid 0 partitions using the perc
> 4 hardware.
>
> The problem is - reading from the disk, and writing to the tape is
> pathetically slow.
> The specs say I should get around 80Mbyte/second - in reality - is about
> 500 Kbytes/second
>
> Writing just to tape, using /dev/zero as input and dd to write, I can
> get up to 60Mybte/second, indicating that the tape drive and scsi card
> is functional from a hardware perspective. Since I can read and write
> data to the disks - I assume that they are functional.
> The files are 80Mybtes for the minimum size that I am writing to tape.
>
> DELL Support hides behind the fact that CENTOS is not a supported OS,
> But RED HAT is - so switch to it, so DELL can get RED HAT Support
> involved. And the fact that Rocks is a modification to an unsupported
> OS....
>
> I have tried using various block size in tar from 256 to 8192 - with
> minimal success.
>
> Does anybody have any experience on setting the OS/Kernel parameters to
> utilize the hardware at something more then a snails pace?
> Or
> Suggestions on what I could test and/or try?
> Or
> Is there a standard disk / tape IO test package that could test the
> speed/performance of the disks and /or tapes?
>
> Thanks for your help
> Dan A. Dansereau
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-- 
Alain Spineux
aspineux gmail com
May the sources be with you