external raid arrays

Chris Black cblack at EraGen.com
Thu Feb 21 14:38:32 PST 2002


On Thu, Feb 21, 2002 at 04:16:20PM -0600, Dave Wright wrote:
> 
> From your description, the request sizes make a big difference as to how to
> configure a filesystem. You probably want latency not bandwidth. Stripping
> and RAID 3 or 5 will probably be bad. JBOD 0+1 is most likely better. A
> RAID has different performance for different request sizes. Kinda like a
> frequency response.
> 
> You probably want to get into JBOD with 15000rpm scsi drives.
> 

What is JBOD 0+1? I have seen JBOD supported but thought it was "Just 
a Bunch of Disks", no striping, mirroring or parity. Why do you say 
RAID5 would be bad? From one RAID vendor I heard that there was little 
to gain on db servers from going to raid 0+1 other than increased 
redundancy. Lots of the operations are not short SQL queries, but 
dumps and imports. These are what take a long time and shuffle the 
most data around.

Chris
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