>To summarise, putting 28 disks in a single vdev is nothing you would do if you 
>want performance. You'll end >up with as many IOPS a single drive can do. 
>Split it up into smaller (<10 disk) vdevs and try again. If you need >high 
>performance, put them in a striped mirror (aka RAID1+0) 
>A little addition - for 28 drives, I guess I'd choose four vdevs with seven 
>drives each in raidz2. You'll loose >space, but it'll be four times faster, 
>and four times safer. Better safe than sorry.... 

Ok... so we've rebuilt the pool as 14 pairs of mirrors, each pair having one 
disk in each of the two JBODs. Now we're getting about 500-1000 IOPS (according 
to zpool iostat) and 20-30MB/sec in random read on a big database. Does that 
sounds right? 
At first, it seems low. Can you try to bench mark that with bonnie++ or iozone? 
You should be getting tenfold of that performance even for database usage 

Vennlige hilsener / Best regards 

roy 
-- 
Roy Sigurd Karlsbakk 
(+47) 97542685 
r...@karlsbakk.net 
http://blogg.karlsbakk.net/ 
-- 
I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er 
et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av 
idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og 
relevante synonymer på norsk. 
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