Are large RAID stripe sizes useful with FreeBSD?
ivoras at freebsd.org
Mon Mar 31 13:19:06 PDT 2008
On 31/03/2008, Xin LI <delphij at delphij.net> wrote:
> Ivan Voras wrote:
> > Most of new hardware RAID controllers offer stripe sizes of 128K, 256K
> > and some also have 512K and 1M stripes. In the simplest case of RAID0 of
> > two drives, knowing that the data is striped across the drives and that
> > FreeBSD issues IO request of at most 64K, is it useful to set stripe
> > sizes to anything larger than 32K? I suppose something like TCQ would
> > help the situation but does anyone know how is this situation usually
> > handled on the RAID controllers?
> Short answer: yes. Larger stripe sizes would allow better performance
> for continuous read/write. In theory they will negatively affect small
> size read/write but in practice you will notice that larger stripe size
> would give better performance in almost all cases.
Ok, I'm interested in how it works. Are the IO requests queued at the
controller until there's enough of them to write a stripe block?
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