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Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

 
Yogeeraj_1
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

hi,
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To me, /dev/.... looks no different then /d01/oradata, they are just files after all.
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I have been using both. For instance, if you consider online redo logs - You never touch online redo logs for anything -- so they are safe on raw (and benefit the most from it -- write intensive)...
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I've also seen ardent fans who always prefer putting a system together to always go for raw. The reasons being:
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a) a PIO as reported as Oracle is very likely to be a real PIO, so you get a true picture of whats going on
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b) the buffering is controlled by Oracle so as a DBA I have more control over it, and Oracle should yield smarter buffering, since it knows thing like extent and segment boundaries
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c) you typically get some benefits from the OS layer (kernelised aio etc)
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d) you do *not* get autoextend. Seeing this as a benefit because it forces you to do some decent sizing and planning up front (sadly lacking in many databases)
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The historical arguments against raw were always management, administrators, etc, but nowadays, every OS as a simple GUI or equivalent to resize them, move them, create/drop them as if they were file systems anyway.
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Many people "afraid of raw" -- like it is "harder". Perhaps that is because the DBA needs SA help to set things up (needs root everynow and again) and they feel a loss of control. Or, they really don't understand what RAW means. A major "fear" for OPS/RAC adopters has always been "oh, i have to use raw". We had to create a cluster file system just to work around that!
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hope this helps too!
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regards
Yogeeraj

No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
Khalid A. Al-Tayaran
Valued Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.


Hi,

We have Oracle 8i (8.1.7.4). All Oracle data files are mounted on file systems. Raw file systems as I recall reading from this forum have the advantage of speed. But it is not much of a difference. You can go with file systems with no worries.

More reading:
http://dbforums.com/arch/165/2001/10/810473

Graham Cameron_1
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

We run 817 and 9024 under filesyestem.
In the past (remember OPS), we have used raw file systems but the unix management effort was too great, as was the difficulty in providing dev and test systems which truly mirrored live.
Technically it may not be compelling, but from a business point of view it is a no-brainer - the company would need a platoon oif unix guys to maintain all environemnts on raw. (Last count > 10 production databases and >100 pre-prod)
-- Graham
Computers make it easier to do a lot of things, but most of the things they make it easier to do don't need to be done.
Stefan Farrelly
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

Weve got dozens of servers all running Oracle and we only use filesystems, not raw, for the simple reason its a lot easier to administer. If its a filesystem the Unix admins can look after it, if its raw the Oracle DBA's need to look after it, and ocassionally when we get a problem or corruption no more DBA's blaming admins and vice versea - better to keep it all under one teams control - the Unix admin team. If there is a problem is far easier for one team to control and diagnose and fix it.

I wouldnt trust our DBA's or even our junior admins with raw - too easy to make a mistake, think a volume is free when it isnt, and accidentally blast it. Ive seen it happen too many times...
Im from Palmerston North, New Zealand, but somehow ended up in London...
Steven E. Protter
Exalted Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

Very good Oracle fans. Its good to see your thoughts, and the more the merrier.

I'll have my dba look at the thread later today.

SEP
Steven E Protter
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A. Clay Stephenson
Acclaimed Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

I seem to be one of the few whacko's who actually believes in measuring the performance. I've done it and my results depended much more on the OS than on the Oracle version. In 10.20 there was about an 18-20% boost in using raw/io --- mainly because by decreasing the size of the buffer cache you could increase the size od the SGA on memory-limited boxes. On 11.0 boxes the benefits of raw vs. cooked were typically about half that of 10.20 (9-10%). On 11.11, the situation reversed and the best performance resulted from cooked files for everything.

If using raw/io, I've found that in all cases, do it for datafiles and indices but leave the archive and redo logs as cooked files.

By the way, there is a way to have your cake and eat it too and that is to use the OnlinewJFS options convosync=direct,mincache=direct,nodatainlog mount options. These have the effect of completely bypassing the buffer cache and the performance is all but indistinguishable from true raw i/o. You can then easily test the difference simply by changing the mount options and restarting Oracle.

NOTE: None of this applies to Oracle RAC. Although there is a Veritas filesystem designed to work across hosts I would never fully trust it and would only use raw/io.
If it ain't broke, I can fix that.
Sandro Schaer_1
Advisor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

all our oracle databases are running on filesystems. it's far easier to manage. especially mirroring across multiple storage systems or moving from one to another.

to gain a bit of performance one really needs to know where to place the files on the raw devices. otherwise it might happen to overload such a devices. talk about io contention.

usually the peformance gain by tuning the application programm is more significant than any hardware tuning. somewhere on oracle's website they have a list on how to get better performance. hardware tuning (filesystems vs. raw devices) is #10.


Mark Grant
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

SEP

I don't have much to offer here apart from marvelling at Mr A Clay again except to say that our DBA's run all these version of oracle and very much insist we go the cooked route.

8.1.7 8.1.7.4 9.0.1.4 9.2.0.2.0 9.2.0.4.0
8.1.7.3 9.0.1 9.2.0.1.0 9.2.0.3.

Again, I believe it's mostly for administration purposes, we really like to be sure that we can determine what a disk is being used for by referencing LVM.
Never preceed any demonstration with anything more predictive than "watch this"
Leif Halvarsson_2
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

Hi,
If you are interested in Oracle performance you sould perhaps have a look at Veritas Database Edition for Oracle.

http://www.veritas.com/products/category/ProductDetail.jhtml?productId=oracleedition


From the product description:

"VERITAS Database Edition includes a unique database accelerator that delivers raw device speed with the administrative ease of traditional file systems."
Claudio Cilloni
Honored Contributor

Re: Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

We use datafiles on filesystems. Once we spent some time thinking about this choice, and the manageability of files over logical volumes was the key factor for this decision. Reading here that there isn't so much difference make me feel good :-).

Sometimes it is useful to copy datafiles for cloning/test/do some kind of experiments; easier than copying logical volumes (we haven't big databases - 10 or 20 GB).

Ciao
Claudio