Re: Dell Perc 5/i Performance issues

/dev/random and /dev/urandom are relatively slow and are not suitable
as the source of data for testing modern hard drives' sequential
throughput.

On my 3GHz dual-core amd63 box both /dev/random and /dev/urandom max
out at ~80MB/s while consuming 100% CPU time on one of the processor
cores.
That would not be enough to saturate single disk with sequential writes.

--Artem



On Sun, Jun 20, 2010 at 9:51 AM, oizs <oizs_at_freemail.hu> wrote:
> I've tried almost everything now.
> The battery is probably fine:
> mfiutil show battery
> mfi0: Battery State:
>  Manufacture Date: 7/25/2009
>    Serial Number: 3716
>     Manufacturer: SMP-PA1.9
>            Model: DLFR463
>        Chemistry: LION
>  Design Capacity: 1800 mAh
>   Design Voltage: 3700 mV
>   Current Charge: 99%
>
> My results:
> Settings:
> Raid5:
> Stripe: 64k
> mfiutil cache 0
> mfi0 volume mfid0 cache settings:
>      I/O caching: writes
>    write caching: write-back
>       read ahead: none
> drive write cache: default
> Raid0:
> Stripe: 64k
> mfiutil cache 0
> mfi0 volume mfid0 cache settings:
>      I/O caching: writes
>    write caching: write-back
>       read ahead: none
> drive write cache: default
>
> Tried to play around with this as well, with almost no difference.
>
> Raid5
> read:
> dd if=/dev/mfid0 of=/dev/null bs=10M
> 1143+0 records in
> 1143+0 records out
> 11985223680 bytes transferred in 139.104134 secs (86160083 bytes/sec)
> write:
> dd if=/dev/random of=/dev/mfid0 bs=64K
> 22747+0 records in
> 22747+0 records out
> 1490747392 bytes transferred in 23.921103 secs (62319342 bytes/sec)
>
> Raid0
> read:
> dd if=/dev/mfid0 of=/dev/null bs=64K
> 92470+0 records in
> 92470+0 records out
> 6060113920 bytes transferred in 47.926007 secs (126447294 bytes/sec)
> write:
> dd if=/dev/random of=/dev/mfid0 bs=64K
> 16441+0 records in
> 16441+0 records out
> 1077477376 bytes transferred in 17.232486 secs (62525939 bytes/sec)
>
> I'm writing directly to the device so im not sure any slice issues could
> cause the problems.
>
> -zsozso
> On 2010.06.20. 4:53, Scott Long wrote:
>>
>> Two big things  can affect RAID-5 performance:
>>
>> 1. Battery backup.  If you don't have a working battery attached to the
>> card, it will turn off the write-back cache, no matter what you do.  Check
>> this.  If you're unsure, use the mfiutil tool that I added to FreeBSD a few
>> months ago and send me the output.
>>
>> 2. Partition alignment.  If you're using classic MBR slices, everything
>> gets misaligned by 63 sectors, making it impossible for the controller to
>> optimize both reads and writes.  If the array is used for secondary storage,
>> simply don't use an MBR scheme.  If it's used for primary storage, try using
>> GPT instead and setting up your partitions so that they are aligned to large
>> power-of-2 boundaries.
>>
>> Scott
>>
>> On Jun 18, 2010, at 6:27 PM, oizs wrote
>>
>
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