Re: tuning, many small files, small blocksize

[Hannes Dorbath <light@theendofthetunnel.de>]

Jeff Breidenbach wrote:
> The underlying disks use linux software RAID-1
> manged by mdadm with 5X redundancy. E.g. 5 drives that
> completely mirror each other.

That's maybe a bit paranoid, but on the other hand it should give good 
parallelism.

> a) Should I just go with the 512 byte blocksize or is that going to be
> bad for some performance reason? Going to 1024 is no problem,
> but I'd prefer not to waste 20% of the partition capacity by using 4096.

I don't think there is performance problem with 512 byte block size, but 
it limits the internal log size to 32MB. You might want to use a larger 
external log.

> b) Are there any other mkfs.xfs paramters that I should play with.

mkfs.xfs -n size=16k -i attr=2 -l lazy-count=1,version=2,size=32m -b 
size=512 /dev/sda

mount -onoatime,logbufs=8,logbsize=256k /dev/sda /mnt/xfs

Requires kernel 2.6.23 and xfsprogs 2.9.5. As said, you might want to 
use an external log device.


-- 
Best regards,
Hannes Dorbath