Gmirror/graid or hardware raid?

[Charles Swiger]

On Jul 9, 2015, at 7:32 AM, Paul Kraus <paul at kraus-haus.org> wrote:
> On Jul 8, 2015, at 17:21, Charles Swiger <cswiger at mac.com> wrote:
[ ... ]
>> Most of the PROD databases I know of working from local storage have heaps of
>> RAID-1 mirrors, and sometimes larger volumes created as RAID-10 or RAID-50.
>> Higher volume shops use dedicated SAN filers via redundant Fibre Channel mesh
>> or similar for their database storage needs.
> 
> Many years ago I had a client buy a couple racks FULL of trays of 36 GB SCSI drives (yes, it was that long ago) and partition them so that they only used the first 1 GB of each. This was purely for performance. They were running a relatively large Oracle database and lots of OLTP transactions.

I seem to have memories of very expensive 18GB and 36GB 15K RPM Seagate Barracuda drives with SCA-2 connectors filling racks full of Sun E450s serving similar roles.  :-)

>>> I thought about zfs but I won't have lots of RAM avaliable
>> 
>> ZFS wants to be run against bare metal.  I've never seen anyone setup ZFS within
>> a VM; it consumes far too much memory and it really wants to talk directly to the
>> hardware for accurate error detection.
> 
> ZFS runs fine in a VM and the notion that it _needs_ lots of RAM is mostly false. I have run a FBSD Guest with ZFS and only 1 GB RAM.

No doubt FreeBSD + ZFS + low memory has improved from what it once was.  But I also suspect that if you did something on the system which put a significant amount of memory pressure on that 1GB VM, it would handle such a load significantly better using UFS than using ZFS.  That's a claim without #s, but someone with such a setup could run some benchmarks if they wanted to compare.

[ ...The rest of your post was informative, and hopefully helpful to the OP as well-- but snipped since I don't have more specific things to say in reply.... ]

Regards,
-- 
-Chuck