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From: Lusotec on 31 Jul 2010 12:29
Rahul wrote:
> Lusotec wrote:
>> iSCSI is SCSI tunneled over IP. So, as long as the IP packets can
>> travel from the server to the disk, iSCSI should work. Directly
>> connecting the disk to the server by a ethernet cable should work just
>> as well (or better).
>
> Thanks! So, does each iSCSI device get a IP address just like any other
> device on the network?

Yes.

> And can iSCSI and TCP etc. traffic be over the same
> physial network or does it need it's own dedicated network.

Yes, iSCSI uses standard IP traffic and can share the network with any other
IP traffic. Just keep in mind that performance will be affected.

> I remember from a long time ago that for plain ethernet traffic one needed
> a special ethernet crossover cable for a direct connection of two servers
> (without an intervening switch). How come the same issue doesn't crop up
> if I try a direct server-to-iSCSI-device connection?

Most (all?) recent hardware correctly auto detects the type of cable so that
is most likely not an issue.

Regards.

From: Marc Haber on 1 Aug 2010 05:02
Rahul <nospam(a)invalid.invalid> wrote:
>Thanks! So, does each iSCSI device get a IP address just like any other
>device on the network? And can iSCSI and TCP etc. traffic be over the same
>physial network or does it need it's own dedicated network.

In Theory, they can, but you'll want Jumbo Frames on the iSCSI
network, and these need to be enabled on a by-broadcast-domain basis.

Greetings
Marc
--
-------------------------------------- !! No courtesy copies, please !! -----
Marc Haber | " Questions are the | Mailadresse im Header
Mannheim, Germany | Beginning of Wisdom " | http://www.zugschlus.de/
Nordisch by Nature | Lt. Worf, TNG "Rightful Heir" | Fon: *49 621 72739834
From: Marc Haber on 1 Aug 2010 05:03
Lusotec <nomail(a)nomail.not> wrote:
>Most (all?) recent hardware correctly auto detects the type of cable so that
>is most likely not an issue.

Most. Auto MDI/X is only mandatory for Gigabit Ethernet, and it is
theoretically possible that a standard-conforming device does auto
MDI/X on GE but not on FE. And there is stil a share of FE-only
devices in the low-cost segment.

Greetings
Marc
--
-------------------------------------- !! No courtesy copies, please !! -----
Marc Haber | " Questions are the | Mailadresse im Header
Mannheim, Germany | Beginning of Wisdom " | http://www.zugschlus.de/
Nordisch by Nature | Lt. Worf, TNG "Rightful Heir" | Fon: *49 621 72739834
From: Rahul on 1 Aug 2010 13:16
Marc Haber <mh+usenetspam1002(a)zugschl.us> wrote in news:i33d6d$ja6$1
@news1.tnib.de:

> Rahul <nospam(a)invalid.invalid> wrote:
>>Thanks! So, does each iSCSI device get a IP address just like any other
>>device on the network? And can iSCSI and TCP etc. traffic be over the
> same
>>physial network or does it need it's own dedicated network.
>
> In Theory, they can, but you'll want Jumbo Frames on the iSCSI
> network, and these need to be enabled on a by-broadcast-domain basis.
>
>

We already have jumbo frames on our LAN. MTU=9000.

Based on the performance caveats though, I think I'll just use a direct
Gigabit link : i.e.

Server<->iSCSI box

No switch. Then I just need to set the right MTU at each end.

--
Rahul
From: Lusotec on 1 Aug 2010 13:51
Marc Haber wrote:
> Lusotec wrote:
>>Most (all?) recent hardware correctly auto detects the type of cable so
>>that is most likely not an issue.
>
> Most. Auto MDI/X is only mandatory for Gigabit Ethernet, and it is
> theoretically possible that a standard-conforming device does auto
> MDI/X on GE but not on FE. And there is stil a share of FE-only
> devices in the low-cost segment.

It never crossed my mind to use Fast Ethernet (100 Mbps) to connect iSCSI
devices. Even Gigabit Ethernet bandwidth (1000 Mbps) is limiting when doing
sequential reads on the majority of recent HDD.

Regards.

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