Re: Needing advice about ZFS and SAN LUNs

Heinz Müller wrote:
Hi,

I've got three 50GB SAN LUNs from an EMC box.
Within the EMC Box the three LUNs were generated from a RAID-5.

For my database ( SYBASE ) I need about 40GB.

My first thought was to take a complete LUN in a zpool
and generate different ZFS volumes for my database.

However, my colleague advises me, to create a slice of about
13GB on each LUN and put them together to a zpool to
get about 40GB for my database. He's understanding is that
the I/O throughput should be better.

I'm not familiar with ZFS so I would like to know which
of the two ways is the better one, because at the end of the day
all I/O is generated in the RAID-5 of the EMC Box.

Thanks!

Heinz




You didn't say what database you are using so I will assume Oracle.

AIRC, the minimum recommended configuration is a minimum of five independent disk drives for use by Oracle. Oracle makes specific recommendations and you may need more than five disks but not fewer if you want decent performance. It also helps to have multiple disk controllers.

EMC^2 is about the most expensive storage on the planet! It's also the most reliable and it gives pretty good performance. It is, as you noted, RAID. Either RAID 1 (mirroring) or RAID 5 is possible. ISTR that EMC^2 disk hardware uses large, 50GB to 150GB (maybe bigger than that now) physical drives and presents several smaller logical drives (LUNs). EMC^2 uses a large RAM based cache to enhance performance. It's my understanding that ZFS creates RAID sets in "software RAID". I don't know if you can turn this off or not. Software RAID on top of hardware RAID may have some performance problems; but I never felt the need to try it.

The EMC^2 command language makes James Joyce "Finnegans Wake" look like a model of clarity.
.

Relevant Pages

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