On 2020.09.15. 11:22, Linda A. Walsh wrote:
On 2020/09/10 07:40, Miloslav Hůla wrote:
I cannot verify it, but I think that even JBOD is propagated as a
virtual device. If you create JBOD from 3 different disks, low level
parameters may differ.
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JBOD allows each disk to be seen by the OS, as is. You wouldn't
create JBOD disk from 3 different disks -- JBOD would give you 3 separate
JBOD disks for the 3 separate disks.
So for your 16 disks, you are using 1 long RAID0? You realize
1 disk goes out, the entire array needs to be reconstructed. Also
all of your spindles can be tied up by long read/writes -- optimal speed
would come from a read 16 stripes wide spread over the 16 disks.
What would be better, IMO, is going with a RAID-10 like your subject
says, using 8-pairs of mirrors and strip those. Set your stripe unit
for 64K to allow the disks to operate independently. You don't want
a long 16-disk stripe, as that's far from optimal for your mailbox load.
What you want is the ability to have multiple I/O ops going at the same
time -- independently. I think as it stands now, you are far more likely
to get contention as different mailboxes are accessed with contention
happening within the span, vs. letting each 2 disk mirror potentially doing
a different task -- which would likely have the effect of raising your
I/O ops/s.
Running raid10 on top of raid0 seems really wasteful
You create individual raid0 from each individual disk, write buffers
off, of course. That is how it's going on sh***y controllers. For some
controllers, firmware upgrade will add JBOD, for some you need to flash
IT firmware, for some you can switch to HBA mode.
But anyway - use HBA or GOOD RAID controller.
--
KSB
