Re: SCSI vs SATA

At 07:07 PM 4/3/2007, Ron wrote:
>For random IO, the 3ware cards are better than PERC
>
> > Question: will 8*15k 73GB SCSI drives outperform 24*7K 320GB SATA
> II drives?
>
>Nope.  Not even if the 15K 73GB HDs were the brand new Savvio 15K screamers.
>
>Example assuming 3.5" HDs and RAID 10 => 4 15K 73GB vs 12 7.2K 320GB
>The 15K's are 2x faster rpm, but they are only ~23% the density =>
>advantage per HD to SATAs.
>Then there's the fact that there are 1.5x as many 7.2K spindles as
>15K spindles...
Oops make that =3x= as many 7.2K spindles as 15K spindles...


>Unless your transactions are very small and unbuffered / unscheduled
>(in which case you are in a =lot= of trouble), The SATA set-up rates
>to be ~2x - ~3x faster ITRW than the SCSI set-up.
...which makes this imply that the SATA set-up given will be ~4x -
~6x faster ITRW than the SCSI set-up given.

>Cheers,
>Ron Peacetree
>
>
>At 06:13 PM 4/3/2007, jason@ohloh.net wrote:
>>We need to upgrade a postgres server. I'm not tied to these specific
>>alternatives, but I'm curious to get feedback on their general
>>qualities.
>>
>>SCSI
>>   dual xeon 5120, 8GB ECC
>>   8*73GB SCSI 15k drives (PERC 5/i)
>>   (dell poweredge 2900)
>>
>>SATA
>>   dual opteron 275, 8GB ECC
>>   24*320GB SATA II 7.2k drives (2*12way 3ware cards)
>>   (generic vendor)
>>
>>Both boxes are about $8k running ubuntu. We're planning to setup with
>>raid10. Our main requirement is highest TPS (focused on a lot of
>>INSERTS).
>>
>>Question: will 8*15k SCSI drives outperform 24*7K SATA II drives?
>>
>>-jay
>>
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