[Lustre-discuss] xserve raid
Brock Palen
brockp at umich.edu
Thu Oct 18 10:02:19 PDT 2007
On Oct 18, 2007, at 4:42 AM, Andreas Dilger wrote:
> On Oct 17, 2007 15:35 -0400, Brock Palen wrote:
>> We are doing some testing,
>>
>> For a OST with a xserve raid connected to linux, is it better to not
>> have a partition table
>>
>> mkfs.lustre /dev/sda
>>
>> or to have a partition?
>> fdisk /dev/sda
>> mkfs.lustre /dev/sda1
>
> For RAID 5/6 devices we recommend NOT having a partition table.
> The reason
> is that the partition table offsets the data partitions by a small
> amount
> (512 bytes usually) and this causes writes to span multiple RAID
> chunks and
> unnecessary read-modify-write activity.
>
> For best performance, pick a RAID chunk size that divides evenly into
> 1MB (e.g. 4 or 8 data disks + parity). The ldiskfs mballoc code works
> to align the allocation with the RAID chunk size for best performance.
Thanks I will keep this in mind.
I did some basics test, 1MDS 1OST 1raid5 (half a xserve raid) Using
tiobench on 1 client, using no partition table netted about 5MB/s
faster for streaming read/write. I will scale up my tests though and
try some other raid configurations. Thanks for the help.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Principal Software Engineer
> Cluster File Systems, Inc.
>
>
>
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