SCSI Raid

Vanilla_Ice · 24 Apr 2007 at 12:20

Hi,

About to setup a striped RAID array using an Adaptec card bought from OcUK. Should both of my drives be on the same channel or not?

Cheers,

ICE

matja · 24 Apr 2007 at 12:47

As long as you remain within the bandwidth limits, you shouldn't see any effect, adverse or otherwise, between having your drives on the same channel or on separate channels. SCSI will cope fine having 15 drives on a single channel, but it won't be optimal.

You should try not to put more drives on a single channel that there is available bandwidth on that channel, eg:

1x 15k drive ~= 100MB/s on a u160 channel = fine, 60MB/s bandwidth left
2x 15k drive ~= 200MB/s on a u160 channel = not optimal

For best performance :
1x 15k on each u160 channel
2x 10k on each u160 channel
2x 15k on each u320 channel
4x 10k on each u320 channel

Having said that, you _may_ find better performance spreading your drives out equally over the channels you have, then transfers to/from the drive cache will be faster.

Vanilla_Ice · 24 Apr 2007 at 13:04

Ok, thanks for that.

I have 2 x 15K U320 drives and a U320 controller. Will probably just put them on one channel. I'll see how much the cables are first!

Cheers,

ICE

rpstewart · 24 Apr 2007 at 14:04

Vanilla_Ice said:
I'll see how much the cables are first!

I'm going to predict you'll put both drives on one channel

5 drop U320 cables are in the £45-60 range.

matja · 24 Apr 2007 at 14:38

2x 15k drives will be fine on one u320 cable

- your HD's won't be starved of bandwidth, 3 HD's would be the limit before you hit the channel bandwidth bottleneck.

Vanilla_Ice · 25 Apr 2007 at 09:08

Thanks guys.

Been looking at cables and there seems to be a big variation in cost.

What type of cable should I be searching for? Ultra320 to LVD? :confused:

Also, am I correct in thinking the cable needs to be terminated??

Cheers,

ICE

matja · 25 Apr 2007 at 19:38

Ultra320 are LVD, just a type of LVD able to carry Ultra320 signals (higher conductivity, twisted pairs).

Theres basically 3 types of LVD ratings -

Ultra2 Wide - 80MB/s
Ultra3 (u160) - 160MB/s
Ultra-320 (u320) - 320MB/s

They all look similar externally, except the u320's usually always have twisted pairs instead of being flat.

Yea you'll need active terminators, unless the drives have built-in termination (most haven't)

Vanilla_Ice · 25 Apr 2007 at 19:52

Hi,

Thanks fella. have got a cable on order Fingers crossed its he correct type!

Only ~£20 too. I hope its not a wrongen!!!

I will mainly be using my computer for gaming as well as surfiing the web and playing about with photos.

Was thiinking of using a stripe size of either 32k or 64k. Any pointers as to which would suit my needs best?

Cheers,

ICE