[moved] total n00bie desperately in search of answers!

Hi guys,

I recently came in contact with Open-E iSCSI servers and decided to improve my knowledge about this topic so I can set up my clients with iSCSI storage server installations. I got myself an iSCSI Enterprise R3 IDE device and will shortly buy a dedicated system for it (8 drives, 3ware RAID controller...)

Since I am new to iSCSI and its features, I have some rather (I hope) easy to answer questions. Here we go:

1. Hardware: For a well performing iSCSI storage server (well enough to build a client SAN and edit broadcast video - perhaps even HD) capable of bonding up to 4 Gigabit channels (802.3ad with an Intel 1000MT quad port card), I plan on buying an Intel board for socket 775 cpus, add an Intel Core2Duo ~2,4 GHz and 2 gigs of ECC RAM. Looking at RAM pricing these days I wonder if I would benefit from installing more RAM? 4 gigs? 8 gigs? Is this a good idea or do I need to get a multicore Xeon system? Should I go with the new 9650 PCIe RAID controllers by 3ware or should I stick to the 9550 PCI-X version?

2. Online capacity expansion. I understand I can expand the capacity of an existing RAID set with a 3ware controller without having to copy files by adding one disk after another. How will this work with my iSCSI target? Will it discover and display the added capacity?

3. I read somewhere that if I set up a volume and access this one volume from multiple initiators, I will get data corruption, so I need to set up each initiator with its own target. Is this true? I guess only when accessing the same file from multiple initiators. How will I be able to use my iSCSI system as a SAN for multiple client workstations in video postproduction (like Apple Xraid with Xsan?)

4. Is there some sort of idle shutdown for a mounted volume? Will energy saving settings affect the volume when they try to spin down the iSCSI volume?

5. Snapshots. I don't get it. Why is there a time window for a snapshot, not just a single time where a snapshot will be made? I understood snapshots as working like this: I put my original files on the volume and activate snapshots. All changes to my original files will be stored in the snapshot area of the iSCSI target, so if someone messes up and deletes a file or changes a database, I can mount the snapshot share and recover the original.

Example: The snapshot stores changes made to files and I have a 10 GB database where someone removed let's say 400 MB of data and then added 500 MB of false data. The original 10 GB database remains untouched, only these 500 MB of new data are in the snapshot. Restoring the entire original file works by mounting the snapshot share, selecting the day before the desaster, and then restoring the entire file.

I must be wrong, I'm describing deduplication here I guess. Is there a detailed description on how snapshots work?

6. Initiator software for MacOS X. I played around with the free OpenSAN iSCSI initiator for OS X but it seems to lock up from time to time. Whenever I don't access the target for about 10 minutes I can't access it anymore - I get a lock up when I try to copy something on/off the volume. Is the ATTO initiator any better? So far I've only found these two. Of course there will be no original Apple Inc. iSCSI initiator so they can have customers stick to their expensive, yet reliable Xraid technology via FC.



I'd appreciate it very much if you could take the time to help me out with answers! Thanks!!

-- Lars

The iSCSI-R3 Enterprise is a USB module not IDE, so make sure the motherboard has this USB pins available (we ship with an Internal USB cable though).

Your hardware setup looks good to start with for your RAID controller, CPU and RAM (start with 4GB). We have new drivers for the 3Ware so either choice is yours or contact 3Ware to see what they would recommend for growth capacity as this is called migrating. After migrating you need to go into the Console screen in Extended tools CTRL + ALT + X then use the PV Resizing tool. Then go to the Volume Manager (please read the manual for this topic) - then add additional space to your iSCSI volume. You will have to restart the Target Volume so the client will see the added space.

You will need to setup an iSCSI Target for each client as we do not support multiple initiators connecting to the same Target.

There is no setting for an idle shutdown for a mounted volume outside of just removing the Target from the Target Manager then enabling when you need to.

When Snapshot is scheduled to run it is exported via iSCSI and will be visible as new
drive which you shouldn't format. So if you have deleted data then copy from the Snapshot.

When a snapshot is taken the whole data is frozen on your local volume
and any changes you made are written in a Snapshot volume.

When it is fulfilled, the end time taken from schedule is reached, or the
Snapshot is manually closed the changes are committed.

Snapshot uses copy-on-write function to do this and is not continues. General rule for sizing the Snapshot is based on that amount of changes you believe will take place then times 3 for the Snapshot volume size. For example if you will have 50GB of changes then your Snapshot should be 150GB or more as a general rule.

You can test this to get a better understanding with sample data before committing to operations.

Link below to provide a better understanding of COW "Copy on Write" with our Snapshot. Other then that it is very simple.

http://en.wikipedia.org/wiki/Copy-on-write


We do not have deduplication functions.

I have heard the iSCSI Initiator globalSAN v3 is good especially with wire speeds.
Not sure about the lockup does this happen with MS initiator?

Todd,

thanks for bringing light into this for me!

I have the IDE thing, so I posted to the wrong forum (again) I guess - sorry.

Another question about hardware: For my iSCSI server, will more cpu cores or a hi GHz CPU be faster? I don't know how threads are handled in the open-e os when doing scsi->tcpip - so is a 2,6 GHz Intel core2duo (2 cores) faster then a 2,4ghz core2quad (2x2 cores) or vice versa?

About RAM: does RAM work as an additional read/write buffer on the system? If I add 8 GB of RAM, will i have a 8 GB (minus system) RAM cache for burst inputs?

So I need to use a SAN software if I want to have multiple users connect to one huge target - that's fine, I still don't need a metadata controller so I'm off a lot cheaper even if I use 10GB ethernet.


Still unsure about the snapshot issue, I opened a separate post about that. I got the basic technology behind snapshots but still I feel challenged at implementing the right snapshot strategy.

I tested some more with the different initiators. After having several connection lockups with the globalSAN initiator, I started up Parallels Workstation on my Mac and connected my VM to the target (win xp with ms iscsi initiator). I did this yesterday night. This morning, I accessed the target in my VM and it worked like a charm, everything behaved like it should, so I guess it's a globalSAN initiator issue. Oh well.

Yes the iSCSI-R3 Enterprise is a USB module not IDE. All IDE modules are EOL "End of Life" we do not sell this anymore only the iSCS-R3 Enterprise, NAS-R3 Enterprise and DSS.

Many engineers have stated the Dual Cores (fast GHz 3.0 and above) with highest amount of Cache on the CPU is best. The way this works is that our cache uses all available free memory strictly assigned to cache and this will rarely be released during write or read options until you reboot the system. The reason is this makes operations on storage much faster to have it available all the time instead of drawing from it when needed (another wait process that would hinder performance).

Yes you will need SAN software to connect to the same target. This is very expensive software almost 8 times more the cost of our iSCSI product. Look to these companies for more information.

MelioFS:
http://www.sanbolic.com/melio.htm

IBM:
http://www-306.ibm.com/software/tivo...ducts/sanergy/
http://www.ibm.qassociates.co.uk/sto...-san-filesyste
m.htm

StorNext:
http://www.adic.com/ibeCCtpItmDspRte...24&item=121889

SGI:
http://www.sgi.com/products/storage/...e_systems.html

PolyServe
http://www.polyserve.com/

DataPlow SFS
http://www.dataplow.com

Todd,

thanks again for your thorough reply. For my OS X clients, I also found http://www.dieagenten.de/metasan.htm - attractive pricing. I have to fight 1000$/liscense from Apple's Xsan so I guess I'm fine.

OK, so no quadcore but rather a faster dualcore CPU. Thanks!