iSCSI - IET or SAN Melody

[roundorange]

Hi All,

I'm new to VMware and is currently looking at the possible "entry-level" iSCSI solutions to use to get things started with ESX3.

I've looked at quite a number of threads in the sub-forums and the direction appears to be towards SAN Melody on Windows. There is also some very brief/vague mention of Linux IET.

Does anyone have more experience to share with regard to using IET as an iSCSI target? Horror stories? Pitfalls?

How about the "dark side" of SAN Melody? Or is SAN Melody smooth sailing all the way?

I'm also keen to find out more on the strategies you guys are adopting to backup the iSCSI LUNs.

Many thanks in advance!

[admin · Accepted solution]

Does anyone have more experience to share with regard

to using IET as an iSCSI target? Horror stories?

Pitfalls?

I've been using IET on our test kit for ages and not had any issues. If you're Linux savvy it's pretty easy to setup and configure too. Remember you'll need some pretty decent disks in the IET server to get reasonable perfrormance from it. There is no support for IET.

How about the "dark side" of SAN Melody? Or is SAN

Melody smooth sailing all the way?

SAN melody is a much more polished "professional" product imo, but then that's what you'd expect as it costs money where as IET is free! We've also got a SAN melody server and I have found the performance of it to be slightly better than IET - but then it does of course come down to the hardware you're running it on. I believe SAN melody's caching algorithms are much better (not sure if IET uses the servers RAM as SAN cache or not) so on like-for-like hardware it should out-perform IET.

As for setup, like most windows based applications, it's a breeze. It hooks into the Windows Disk Management MMC snap-in and everything is managed via that.

It's also more flexible than IET, you can thin-provision disks (i.e. provision a 2Tb LUN when you only really have say 500GB of disk, you can then add more storage to the pool later without touching the partition), it does snapshots, WAN volume replication, you can run two in an HA configuration to provide path redundancy, live LUN migration, etc. It also supports both iSCSI and FC storage - so you can bring all of your storage under one managment structure.

As I said it's a much more fully featured bit of software - but that's because it costs money. For a free solution IET is great.

I'm also keen to find out more on the strategies you

guys are adopting to backup the iSCSI LUNs.

Couple of options - if you went the SAN melody you could use their volume replication. Or you could use VMware snapshotting and export the data on a VM level rather than a volume level to andother iSCSI box. etc.

Have a read of this.

http://www.vmware.com/pdf/vi3_301_201_vm_backup.pdf

[mcwill]

We dabbled a bit with IET before plumping for SANmelody.

The reason - out of the box SANmelody gave us better performance.

However as IET is free and SANmelody offers a 30 day trial license you can test drive both to see which works best for yourselves.

[wila]

Another way of looking at this choice is to look at your organisation.

Are you guys a windows shop or a linux shop or both?

If you are a windows shop then you might want to stick with windows tools as that is what you are most comfortable with. This way you don't have to directly invest extra time in learning a foreign OS. Especially when you get into "troubleshooting mode".

OTOH, when you are a linux shop / have previous hands on experience / would like to get more comfortable with linux/unix (after all ESX is OS wise more linux as it is windows) then it can be a good choice.

The openfiler solution has been pretty popular here, uses IET under the hood, and just requires compatible hardware, no linux knowledge required in getting it to run.

Most popular distributions also have IET in their repositories. This however would assume that you would use the box for more as just storage and would require some linux knowledge most of the times to get it working.

[roundorange]

Hi Ppl,

Thanks for the inputs. We are primarily a Linux shop and I'm currently testing out VMware with VMs running off a Linux NFS server. The VMs are a mix of Windows and Linux.

I'm exploring the possibility of using iSCSI as that would allow native VMFS filesystem but I'm concerned with the stability of "software" solutions such as IET and/or SAN Melody as if they go south, alot of VMs will be affected (looks ugly).

Anyone encountered deadly issues with IET or SAN Melody or far? i.e. kernel crashes, blue screen of death, etc?

[mcwill]

As far as SANmelody goes it has been stable as a rock since we put it into production (3 months ago), 100% uptime with no restarts.

The important point is to treat the SANmelody server as an appliance not a general server, therefore...

1) Install Win2k3 patch it as necessary then turn off all auto updates.

2) Don't run anything else from the SANmelody box, use it as an iSCSI appliance, nothing else.

Regards,

Iain

[oreeh]

One word of caution: openfiler doesn't use the latest IET code which could lead to problems when using it as a shared storage for ESX hosts (reserve/release and LUN presentation are an example)

[roundorange]

Hi Mcwill,

May I know which version of W2K3 are you running (32 or 64 bit)? And also what are you using to backup the iSCSI luns?

TIA!

[roundorange]

Hi Oreeh,

Thanks for the caution. I've visted the IET mailing archives on SF and it seems that even in the latest IET code, there are some occurance of kernel panic and/or abnormalities?

[oreeh]

I'm currently using (in the testlab!) rev 122 (I know this is not the newest one) without any issues.

Make sure to use a stock kernel from kernel.org

[mcwill]

SANmelody requires a 32bit platform, we are running Win2k3 R2.

As for backing up we don't backup the LUN, currently[/b] we

a) backup snapshots of the VMs to the esx host local vmfs store

b) log ship sql data to an offsite SQL server

c) DFS-R user data and exchange/sql backups offsite

(We may also write the odd tape from time to time)

We are also investigating SANmelody's replication system to maintain a mirrored copy of the LUNs but we haven't put that into production yet.

Message was edited by:

mcwill

[admin]

I've been using IET on FC6 as the shared storage for my test kit for 10 months and not had one problem with it yet.

[roundorange]

Hi Oreeh, \*sigh*, I was hoping to use the stock kernel in either RHEL4 or RHEL5 -> Save some effort in configuring the items to compile into the kernel.

[roundorange]

Hi Mcwill, by (c) DFS-R, are you referring to the NTFS volume within a VM being replicated via DFS to another VM/server elsewhere?

How's SANmelody's performance like so far?

Any idea how it sizes up against the "MS Windows iSCSI" found in their latest "Windows Unified Data Storage Server (WUDSS)"?

[mcwill]

Hi Mcwill, by (c) DFS-R, are you referring to the

NTFS volume within a VM being replicated via DFS to

another VM/server elsewhere?

Not the entire volume, just replicating the contents of certain shares using DFS-R (as provided by win2k3 R2).

How's SANmelody's performance like so far?

Very good, it has far exceeded our initial expections.

Any idea how it sizes up against the "MS Windows

iSCSI" found in their latest "Windows Unified Data

Storage Server (WUDSS)"?

Sorry, I've not come across that target.

[roundorange]

Thanks all, you've been a great help!