Hi
I agree with you on point 4 – and the
SA here also confirms that the Manager has his facts wrong on this point.
I haven’t seen much here in terms of
quantitative measurement of IO – I can ask around. I’d like
to do DBA work, but they have me working on an Data Architecture project (which
is great experience), so I have no time to be a DBA.
Cary Millsap’s paper “Is RAID 5
Really a Bargain”, states that RAID 5 is three times more likely to incur
data loss than a RAID 1 Array. A date says it is Jan. 3, 2000 – so almost 4
years ago. I don’t know if this is still true today or not.
But I would also be interested in more details on this.
Thanks!
Sam.
-----Original Message-----
From: Niall Litchfield
[mailto:[EMAIL PROTECTED]
Sent: November 20, 2003 7:44 AM
To: Multiple recipients of list
ORACLE-L
Subject: RE: SAN configuration for
Banner
I
*think* but I may have entirely misread the comment that point 4 is just wrong.
It sounds like you only have one raid 5 set (which is shared between 2
machines). If this is the case then the clustering has no effect on the fault
tolerance/performance of the raid 5 set. Or am i just on crack here?
Point 5.
writing to the datafiles *may* be acceptable on a raid5 set (it just depends
what the volume of write activity is - does anyone have any idea what the IO
requirements will be? if so do the calculations), writing to redo/archive
almost certainly won't be. I'd hold out for Raid 1 for the logs and maybe
compromise on Raid 5 for the data.
as for
the last point, I'd also like to see the justification for raid5 is 3 times
more likely to suffer dataloss. I'm afraid that a) I don't think I believe it
and b) you've got the logs anyway :( OK just a) really.
corrections
and clarifications welcome.
You may
also wish to look at James Morle's SANE SAN paper at www.oaktable.net it would appear to be
pertinent (and he does know whereof which he speaks)
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Sam
Bootsma
Sent: 19 November 2003 15:55
To: Multiple recipients of list
ORACLE-L
Subject: FW: SAN configuration for
Banner
Hi List,
We are
approaching the cusp of a decision on how to store Oracle data files on our
SAN. We don’t have the SAN yet, but it is due to arrive any week
(if not any day).
I passed
Cary’s “Is RAID 5 Really a Bargain?” paper to our Sys Admin,
which he read and succinctly summarized for the Technical Manager here. I
have also read through a couple of papers referenced in the BAARF site.
The Sys Admin comments were:
Dell would
like to know what RAID mode we want configured on the SAN for the B80 and 6C4
computers. Sam has told me that, in the Oracle community, mirroring (RAID1) is
preferred over RAID 5 for various reasons (RAID5 is: more costly for
write-intensive applications, 3 times more likely to incur data loss,
suffers from massive performance degradation during partial outages). RAID1
will be more costly per unit of usable storage. Mirroring seems to be the best
choice. Let me know what you think.
Here is
the Manager’s response:
Any
suggestions on how I can counter points 4 and 5 – and the last point
before his “Thanks” line? Currently we have two B80’s
(AIX 4.3.3) set up in a HA configuration. They share an external disk
array. So if a hardware component in the primary box fails, then it will
automatically failover to the secondary box (and at the same time, the
secondary box takes control of the external disk array). I think the
clustering term in point (4) is referring to this setup.
Thanks
for any suggestions.
Sam.
Sent: November
18, 2003 5:08 PM
Subject: RE: SAN configuration for
Banner
All the points are
valid...however..my thought processes were as follows:
1. The System &
Core Application disks are resident on the disks within the CPU and Mirrorred
(Everyone OK with that I think)
2. The Databases
are Resident on the SAN
3. The SAN disks
are RAID 5 as the provide more usable space for the cost as compared to
mirrorring
4. As the IBM
Systems (B80's & 6C4's) are clusterd thus effectivley Mirrors the RAID 5
Arrays mitigating the issues Sam raises re preformance degradation (which will
only ever arise in the event of a failed disk/automated rebuild which is
usually configurable to address performance degradation)
5. Write to
Disk/Commit to Database should be a background process (although I recognise
this is a transaction/write intensive based system)
This is a standard model
that all servers are being deployed with and unless there are any specific
technical reasons why this will not work it is the way I would like to see the
systems implemented. Remeber, with the SAN...Reconfiguration of Disks is
not a large issue anymore if required in the future.
Although not an
AIX/Oracle guy...I disagree with the statement that RAID5 is 3 times more
susceptable to incur Data Loss. RAID 5 is a proven technology
-----Original
Message-----
From: Carl Nowak
Sent: Tue 18/11/2003 2:56 PM
To: Andrew Riem
Subject: SAN configuration
for Banner
Dell would like to know what RAID mode we want
configured on the SAN for the B80 and 6C4 computers. Sam has told me that, in
the Oracle community, mirroring (RAID1) is preferred over RAID 5 for various
reasons (RAID5 is: more costly for write-intensive applications, 3 times more
likely to incur data loss, suffers from massive performance degradation
during partial outages). RAID1 will be more costly per unit of usable storage.
Mirroring seems to be the best choice. Let me know what you think.
Carl
