Re: XFS/LVM/Multipath on a single RAID volume

Emmanuel Florac
2015-02-25T11:49:49Z

Le Wed, 25 Feb 2015 09:33:44 +1100
Dave Chinner <david@fromorbit.com> écrivait:

> > On an existing array based on similar but slightly slower hardware,
> > I'm getting miserable performance. The bottleneck seems to be on
> > the server side. For specifics, the array is laid out as a single
> > 26TB volume and attached by a single 3Gbps SAS.
>
> So, 300MB/s max throughput.
>

Ah yes, maybe external RAID controllers can only use one SAS channel
out of the 4 available, that would definitely limit performance badly.
This limitation don't apply to internal RAID controllers (Adaptec, LSI,
Areca) driving a JBOD though.

I'll do a short digression on external storage enclosures: they're
mostly useful to provide redundant controllers. If you're using only one
controller, cheap ones (such as infortrend, Promise and the like) will
always perform poorly compared to a modern PCIe RAID controller.

High-end storage enclosures (DotHill, NetApp, etc) with high-bandwidth
attachments (FC or IB) provide better performance AND redundancy, but
at a hefty price.

So if you want fast, cheap arrays, definitely use Adaptec/LSI/Areca and
simple JBOD chassis like supermicro's.

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