Re: anyone tried NVME in ODA?
- From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 30 Jan 2017 21:04:39 -0500
On 01/30/2017 11:24 AM, Ls Cheng wrote:
Expected to reach same IOPS as ASM on future 12.1.2.10.0 with
fix 24930950.
I don't think it's a reasonable expectation. ACFS is a fairly complex
layer on top of ASM. It is a cluster file system, which means that it
must synchronize FS cache on all nodes that have mounted the file
system. It also has to manage free space, probably using bitmaps. To add
an additional layer, ACFS is an extent based file system, so it also
must manage extent maps and windows. Also, ACFS is implemented as a
userfs, which means that open,close, read and write system services have
another level of indirection to go through, which is not the case with
drivers that are implemented in the kernel.
Long story short, ASM is as close that you can get to raw disk and still
have it manageable. There is a lot that needs to happen on top of ASM,
to present it as a file system. The same is true for raw devices: there
is a lot that needs to happen on top of raw disk, to present it as an
Ext4 or NTFS file system. This is essentially the old debate: is the raw
disk better than the file system, which was all the rage on this list in
the times of oracle 7 and 8. ASM is more complex to manage but provides
better performance. And it always will. I don't expect ACFS to match
the raw ASM performance any time soon. The reason is simple: ACFS is
another complex software layer on top of ASM.
The important question is whether the raw IO performance is more
important than manageability. If your answer is "yes", you will probably
want to use ASM. If your answer is no, you will probably want to use
ACFS. Let's not forget that ACFS has a lot of very desirable goodies
like snapshots, ACL and tagging. There are very good reasons for using
ACFS. It all depends on your priorities.
--
Mladen Gogala
Oracle DBA
Tel: (347) 321-1217
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