Re: md RAID over SATA performance

[Mark Lord]

Even with hardware RAID the numbers I see are not often
much better than this.

Unless O_DIRECT is used (hdparm --direct), in which case they
immediately jump to a level that is more limited by the PCI
and memory speeds of the system.

Eg.  205Mbytes/sec for a 4-drive RAID0 over 64-bit/66Mhz PCI.

I guess the page_cache overhead is rather substantial
for the simple read-a-sequential-block test.

Cheers
--
Mark Lord
(hdparm keeper & the original "Linux IDE Guy")
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