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MaxTheRabbit
02-10-2003, 09:40 AM
If I were to put 3 36.7GB 15000RPM drives in a RAID 5 array on a ultra 160 host adapter would the drives' throughput exceed the 160 MB/sec rate of the host? Will I suffer from not having a u320 host adapter?
BipolarBill
02-10-2003, 12:43 PM
Hardly. The 3rd drive in a RAID 5 array is a parity drive and not very active.

Go for it. :cool:
MaxTheRabbit
02-12-2003, 06:37 PM
sweet, thanks bill
scsiraid
02-16-2003, 07:00 PM
Not true Bill.... Parity is striped across all drives in the array in RAID 5. RAID 3 and 4 dedicated parity to a single drive. In random IO all three drives will be accessed the same amount. As the the base question... Three 15K drives running wide open could theoretically challenge U160 bandwidth but such a workload wouldnt be real. You should be fine.
BipolarBill
02-16-2003, 07:07 PM
Yeah - I've been rolling my eyes since I got that info a few days ago. Because the answer is that same, I didn't see fit to edit or supplement the post.

Good info though. :)
Peter M
02-17-2003, 03:53 AM
I bet you're on a standard PCI bus with a sustained throughput of around 100 MB/s anyway ... so don't get a headache about saturating SCSI. You won't. PCI will be first.

Besides, are you considering running CPU driven RAID 5 on a normal SCSI controller, or is that a real, got-my-own-brain RAID controller card?
MaxTheRabbit
02-18-2003, 10:50 AM
I will be using a real hardware RAID controller. Part of my question is based on wondering what type of bus to get (32bitx33MHz,64bitx33MHz,64bitx66MHz,64bitx100MHz, 64bitx133MHz)
BipolarBill
02-18-2003, 11:09 AM
Originally posted by MaxTheRabbit
Will I suffer from not having a u320 host adapter? Suffer? That's a harsh word. No - you won't suffer. In order to get 64-bit u320, you need a 64-bit/66MHz PCI slot. If you don't have one, it's a moot point.

If you're on "standard" PCI, it's going to be 32-bit/33MHz.
Peter M
02-18-2003, 02:14 PM
You should be going for a single or dual chann U160 RAID controller. I have good experience with ICP Vortex brand controllers. Their older models (with 33 MHz PCI interface) have come down in price quite nicely. And of course they use the lovely LSI Symbios SCSI chips :)