Re: Performance Question: RAID or Individual drives ?

Sheesh, learn to read, bud - rather than just jumping in with what *you* think *I think*. Read on.

SV wrote in message <#JlOD9nr9GA.317_at_upnetnews03>...
>
>If you think what you said is the whole story
>then you're wrong.

No, I never did say that was the whole story. Try and read the first sentence again, where I suggested the poster check his *own* system with his *own transactions*. Also check most of the other posts I mail in here, which also always suggest people test against their own systems.

>
>There are plenty of other things which can
>influence I/O perfomance.
>SCSI controllers (Fast/Wide or Ultra Fast/Wide, or narrow ),
>RAID disk cache configuration (write-back or write-through),
>software or hardware striping,
>OS, etc.

You don't say. Whoa, you're a genius. I'd have never thought those things could make a difference. Not!

>
>You mentioned neither of them, so your numbers
>are pretty much useless for any intent or purpose
>other than for your particular system.

Correct, just like I said. And I've also done some testing on NT, which pretty much gave the same results - and on SCSI.

>
>About the only thing I would agree with out of the box
>is that parallel query does seem to improve total I/O
>disregard of other things.

Hey, we agree on something. Obviously this is where the fault must be.

>
>
>Cordially,
>Sergei
>
>
>
>
>MotoX wrote in message
><900340505.19346.0.nnrp-05.c2de712e_at_news.demon.co.uk>...
>>That was well timed - I'm just in the middle of benchtesting strip v
>>non-strip v single disk v RAID5 for a client. It's a UNIX box, but the
>>outcome *should* be similar on NT. However, *test* you own kit with a mix
>of
>>the types of transactions *you* are going to perform. Anyway, here goes
>>(35,000,000 row test table):
>>
>>READING:
>>
>>One disk, best read rate 10MB/s per disk (one of).
>>
>>3 striped disks, 3.4 MB/s per disk. If parallel query used (degree of 2 or
>>4), rate goes to 5.7 MB/s per disk. In other words, if you stripe (64k),
>>it's also best to use parallel query when you can, because if you don't
you
>>won't max out the I/O bandwidth you've created.
>>
>>On 6 striped disks, 1.95 MB/s per disk. With degree of 2 or 4, 4.4 MB/s
per
>>disk. In other words, still use parallel, and although you continue to get
>a
>>boost, it's reducing.
>>
>>RAID5 - 1 processor, 8.3 MB/s per RAID set. Parallel with degree of 2 or
4,
>>16.9 MB/s per RAID set. In other words, for reading, RAID5 is just as
quick
>>as striped disks, but you still need to go parallel to max out the I/O.
>And,
>>of course, RAID5 (like striping) is much faster than non-RAID single
disks,
>>as long as you can provide the CPU to drive it.
>>
>>WRITING (in summary as I haven't finished yet):
>>
>>3 striped drives are about twice as fast as a single disk (not three times
>>faster).
>>6 striped drives are about 4.5 times faster than a single disk.
>>NB. Like reading, the overhead of sync'ing the drives, memory bandwidth,
>>etc., affects how much real improvement you get - it won't be linear as
you
>>add more drives.
>>
>>RAID5 - on my limited testing so far, writing (creating a 4 Gig
tablespace)
>>has dropped from 3 x 6.8 MB/s per disk to 7.5 MB/s per RAID set. In other
>>words, RAID5 array is over twice as slow on heavy writing as the same
disks
>>striped (non RAID5).
>>
>>In summary, look at striped disks (RAID0 or RAID0+1 or through an LVM) for
>>write intensive parts of your db. Look at RAID5 for read intensive
>sections,
>>and learn to live with the write penalty where you can.
>>
>>MotoX.
>>
>>
>>
>>
>>
>>Dominic Baines wrote in message <35AA0A1F.41151B15_at_hermes.cam.ac.uk>...
>>>I've an NT admin who RAID's everything on every NT box he touches. This
>>>is OK for redundancy if the system dies but I'm not sure this is the
>>>best option for an Oracle database performance reasons mainly. Are there
>>>any tuning guru's out there who could shine a like on the appropriate
>>>arguament to use IF it would be better to use individual drives rather
>>>than to rely on the RAID set ?
>>>
>>>What am I talking about ?:
>>>
>>>Standard set-up would be an Oracle server on NT 4 SP3 with system disk
>>>a mirrored pair and second 'drive' being a raid set over say 7 to 15
>>>disks. So ORANT is on D:, as is everything else. OK there are different
>>>drives and spindles but every read or write to anywhere on the RAID set
>>>would use every drive, wouldn't it ? These are 4GB Seagate SCSI drives.
>>>The controller is a proper RAID controller, whatever that may be. It's
>>>all on Compaq kit.
>>>
>>>Thanks,
>>>
>>>Dominic Baines
>>>
>>
>>
>
>
Received on Tue Jul 14 1998 - 02:06:21 CDT