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From: Rahul on 30 Jul 2010 23:59
How's the support for eSATA in Linux? I've never worked with eSATA before
so I was wondering. I run CentOS 5.4. Just wanted to get some opinions
before I spent my $$ on one such device.

Also, are eSATA devices visible just like SATA or SAS as block devices?
Will I see a /dev/sda /dev/sdb x8....etc. if I buy a 8bay eSATA storage
box?

On a related note I know that iSCSI is used a lot with Linux servers these
days. But I am still confused about the exact connections between the
server and the iSCSI storage? Googling+wikipedia reveal that in SAN's etc.
they have a whole dedicated switching network but if I just bought an iSCSI
storgae device to attach to my dedicated server can I just hook the two
together with a ethernet cable? Or will I have to put a switch between?

[In case you wonder why I'd even consider iSCSI in the absence of a SAN:
Some nice and reasonably priced boxes I saw offer iSCSI as a connection
option. So I am curious.]


--
Rahul
From: Grant on 31 Jul 2010 02:06
On Sat, 31 Jul 2010 03:59:19 +0000 (UTC), Rahul <nospam(a)nospam.invalid> wrote:

>How's the support for eSATA in Linux? I've never worked with eSATA before
>so I was wondering. I run CentOS 5.4. Just wanted to get some opinions
>before I spent my $$ on one such device.

Just another SATA drive. eSATA is a hardware spec. If you have the
mobo controller support, you can 'eject' the hard drive and disconnect
it.

I dunno about iSCSI.

Grant.
From: Lusotec on 31 Jul 2010 08:12
Rahul wrote:
> How's the support for eSATA in Linux? I've never worked with eSATA before
> so I was wondering. I run CentOS 5.4. Just wanted to get some opinions
> before I spent my $$ on one such device.
>
> Also, are eSATA devices visible just like SATA or SAS as block devices?
> Will I see a /dev/sda /dev/sdb x8....etc. if I buy a 8bay eSATA storage
> box?

From software perspective eSATA is just like SATA, and Linux has excellent
support for it. Hardware support is needed, obviously.

> On a related note I know that iSCSI is used a lot with Linux servers these
> days. But I am still confused about the exact connections between the
> server and the iSCSI storage? Googling+wikipedia reveal that in SAN's etc.
> they have a whole dedicated switching network but if I just bought an
> iSCSI storgae device to attach to my dedicated server can I just hook the
> two together with a ethernet cable? Or will I have to put a switch
> between?
>
> [In case you wonder why I'd even consider iSCSI in the absence of a SAN:
> Some nice and reasonably priced boxes I saw offer iSCSI as a connection
> option. So I am curious.]

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).

Regards.

From: Rahul on 31 Jul 2010 11:53
Lusotec <nomail(a)nomail.not> wrote in
news:i313ur$3ks$1(a)news.eternal-september.org:

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

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?

--
Rahul
From: Aragorn on 31 Jul 2010 12:02
On Saturday 31 July 2010 17:53 in comp.os.linux.hardware, somebody
identifying as Rahul wrote...

> Lusotec <nomail(a)nomail.not> wrote in
> news:i313ur$3ks$1(a)news.eternal-september.org:
>
>> 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?

As I understand it, the iSCSI controller would have one IP address.

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

That should be possible, although it could impede performance.

> 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 modern switches and routers have automatic detection for whether a
regular or crossover cable is being used, so I would suspect that iSCSI
controllers have the same capability built-in.

--
*Aragorn*
(registered GNU/Linux user #223157)
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