This is sort of long so bear with me...
TL;DR: Who has compared ASM vs. dNFS (not used together) and what did you
choose and why?
I was wondering if anyone on the list has opinions on, or has evaluated, ASM
vs. dNFS in a mutually exclusive configuration for datafile/arch/ctl/redo
storage?
We have been using ASM on NetApp over fiber channel for many years now with
great success. We particularly like the ability to add/remove spinning disks
or SSD on the fly. We can even "upgrade" our filers with no down time by
adding in and removing LUNs and letting ASM do it's rebalance thing.
Recently, some new technology changes have become available for us. These
changes are in the form of moving our compute platform to UCS/Flexpod
environments and the introduction of VMware. Operating on the UCS gives us
access to 10gE (currently our infrastructure is primarily 1gE) which brings the
option of using dNFS to the table.
Now, I am just starting down the path of comparing the two for pluses and
minuses and I do not have all the data yet. Thought I would reach out to the
list.
There are a few things that attract us to dNFS:
1. Less complication...maybe? In RAC environments, I still think we need
ASM for OCR/Voting...someone correct me if I am wrong. But, we will not have
to manage ASM disk groups like we do now. However, after so many years of
using ASM, our team is pretty well versed in it...so, is it really an added
complication?
2. Better ability to use NetApp snapshots:
a. We can do file level recovery with dNFS which cannot be done with ASM
b. Right now we have to manage separate disk groups for each database
(when we have multiple databases on a node/cluster) if we want to use NetApp
snaps since restore is done all-or-nothing at the disk group level. In some
cases, we have hit the maximum number of disk groups (63) in ASM. I think
multiple disk groups like this also results in more overheard managing and
monitoring. Furthermore, more disk groups seems to waste more space as it is
sometime hard to predict storage needs...I think in the end the best approach
is to over allocate storage instead of having to manage it constantly.
3. Our primary OS platform is OELinux x86-64. Linux has a LUN path limit
of 1024. That sounds like a lot, but, with multiple LUNs per disk group and
multipathing in place, each disk group takes up a minimum of 8 LUNs. This is
not to mention LUNs supporting the OS and shares. Since we need to have
separate disk groups for each database to support snaps, a cluster with a lot
of compute power will either hit the LUN path limit or the ASM disk group limit
before we run out of compute. My understanding is that we do not have this
limit problem with dNFS.
4. It seems that dNFS will lend itself better to VMware:
a. Setting up snaps with ASM on VMware led us down the path of using
RDM's (which have limits feature wise) instead of VMDK's.
b. VMDK's with dNFS seems like less configuration which will allow for
quicker provisioning on VMware. VMDK's are also the preferred approach
according to VMware.
c. Using ASM and LUNs with VMware still is an issue with the 1024 LUN
path limit. However, it moves to the physical hosts in the ESX cluster...not
just the guest OS. Therefore, we are seriously limiting the number of guest
OS's on our ESX clusters before we run out of compute because will hit the LUN
path limit first.
So, that's it in a nutshell. I am sure there is a lot more to it but I
appreciate any input people may have.
Thanks,
Chris..
_____________________________________________________________________
Chris Ruel * Oracle Database Administrator * Lincoln Financial Group
cruel@xxxxxxx<mailto:cruel@xxxxxxx> * Desk:317.759.2172 * Cell 317.523.8482
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