On Wed, Oct 21, 2009 at 10:36 AM, Rainer Duffner rainer@ultra-secure.de wrote:
Rudi Ahlers schrieb
John, you're right. iSCSI isn't an SMB replacement as I have learned through all of this. SMB is good for sharing data between many PC's, and even servers, but from what I understand it's also slower that iSCSI and won't allow me to scale the storage by simply adding another cheap server to the network. With iSCSI I could / should be able todo that.
iSCSI is just a protocol. It doesn't say anything about the underlying storage. http://en.wikipedia.org/wiki/ISCSI
You can have a SAN (HP EVA, EMC, whatever) and still have that served via iSCSI by an additional piece of hardware you buy. Or you can have a NAS like NetApp and buy another of those ridiculously expensive licenses and then you can server iSCSI with that, too.
What your storage looks like doesn't matter. The initiators just talk the iSCSI-protocol to the target.
OR am I approaching this from a different angle? If I wanted to setup a server to serve content (in this case file storage, www, email & SQL) to a network of computers, would iSCSI have served the purpose?
Yes. Allthough, as iSCSI uses the ethernet-network, you need good switches. Because, your actually data-traffic has to go through the same network.
Or should I have kept using SMB? I am looking for a way to quickly expand the whole setup though. If we need more space, then I just want to add another cheap server with a 1TB HDD, and have it available on the network. It is my impression that I could use iSCSI, probably together with XFS, to accomplish this?
No, it doesn't quite work like that. At least, for any trivial setup that doesn't involve some storage-virtualization software.
If you can afford it, NetApp is a good solution for what you want to achieve. Or try one of the new SUN storage boxes.
If that is out of your (financial) league, you can build the same functionality as the SUN OpenStorage boxes with your own hardware and OpenSolaris - although you will not have the extensive analytics and the ease of use of the GUI. I wouldn't use any of the cheap SOHO NASes mentioned before in this thread. Build your own from HP, Dell or IBM hardware and preferably OpenSolaris. (I know, sounds weird on a CentOS-list).
For example: if your cheap "NAS"'s storage controller dies, are you sure that the replacement unit's controller you get can actually read the data? Also, if you have data on iSCSI, you really need hardware with almost no unplanned downtime. Even planned downtime can be difficult to manage, because so many servers depend on the iSCSI-targets and you'd have to shutdown maybe a dozen or more servers for that single reboot.
Centralized storage is nice for management and backup, offers a lot of possibilities regarding efficiency and utilization - but tends to create single points of failure that just don't exist with direct attached storage.
Rainer _______________________________________________
Hi Rainer,
I honestly don't want to spend a lot of cash on a proprietary system like NetApp and actually want to use a lot of old tower machines (i.e. limited space for hard drives, and no redundancy, slower CPU's, etc) we already have. CentOS is my preferred OS of choice, and I don't know Solaris, at all. I could probably give it a go, but not right now.
The setup I'm hoping to achieve is as follows: We develop a lot of PHP + MySQL based intranet and internet applications, so the main server currently runs Apache + PHP + MySQL + Zend, etc.
Some of the applications require large volumes of data which is currently saved on the sambas server. This makes it easy, as any one on the LAN can add / remove data to the SMB server, and the PHP app can also access it. But I still have a problem, that if the storage runs out, and I add another box to the network, then it's a different server with a new storage point - not ideal.
I was hoping with iSCSI to join these storage servers into one large storage volume, together with XFS (or ClusterFS / GclusterFS?) and thus have anyone connect to one "central server", both for development, file storage and even email. Everything runs on Gigabit switches, so that's not a problem, and redundancy isn't the highest issue either.I'm not too concerned with that, for this particular project.
So, trying to use existing hardware, and preferably CentOS (I would prefer not to reinstall the server right now), what else (if iSCSI isn't right) would I rather use,if I want to consolidate the storage of a few Linux machines, and export it over the LAN to various workstations?
Another project altogether though would require a similar setup with cheap central storage server(s) at a data centre - but this will purely be a storage server for XEN virtual machines to connect to, and store backup data. For this OpenFiler works very well at the moment.