PowerVault MD1000 SATA Read Performance Tuning

Greg Dickie greg at max-t.com
Thu Nov 9 07:35:39 CST 2006

Did you try turning on or adjusting the readahead cache. Both on the
Perc5 and then tuning it in LVM. Thats where I would start.


On Thu, 2006-11-09 at 15:54 +1000, mike wrote:
> Hi
> I have recently purchased a MD1000 loaded with 500gb 15x SATA-II NCQ
> disks. It's connected to a PERC5/E in a PE2950 (Dual 5160 Xeon; 16GB RAM).
> Currently it is configured as one RAID-5 array (with global hot spare).
> The application is a popular free HTTP file server, and it is almost
> exclusively reads. We're maxing out at around 20-24MB/s read performance
> from the RAID-5 (serving about 1000 concurrent downloads, 50% of which
> are large ISO images). The files we're serving range from 1KB text files
> up to large 500-600MB ISO images. The small files are served quickly
> while the large files start out ok but slow down, eventually to a crawl.
> I'm wondering what I can do to try and boost this performance.
> So far, I've used the default stripe size (64kB?).
> The filesystem on top is XFS (blocksize is 4kB) and it is mounted -o
> noatime,nodiratime. This filesystem is on top of an LVM logical volume,
> from which I understand the performance hit should be negligible.
> Here's what I have thought of trying so far:
> - Increasing the XFS block size to 64kB (to match the stripe size)
> - Increasing the XFS block size and stripe size to 128kB
> - Not using LVM
> - Trying different cache policies
> - Looking to see if there are any settings relating to SATA-II NCQ that
> can be tweaked
> - Looking into direct i/o under Linux[1]
> If anyone more experienced with storage can offer some insight it would
> be greatly appreciated.
> Cheers
> [1]I'm not sure this is even appropriate here, but I read an article
> (http://developers.sun.com/solaris/articles/tuning_for_streaming.html)
> on Solaris UFS where sun recommended mounting with the 'directio' option
> when dealing with large files.
Greg Dickie
just a guy
Maximum Throughput

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