ZFS + iSCSI architecture

[Fleuriot Damien]

On Feb 19, 2013, at 11:20 PM, "bsd at todoo.biz" <bsd at todoo.biz> wrote:

> Hello,
> 
> 
> I am about to start deploying a large system (about 18 To which can grow up to 36 To) based on a big Intel platform with lot's of fancy features to have turbo boosted platform (ZIL on SSD + system on dongle if I go for FreeNAS). Since I want to move on quite fast I might decide to use FreeNAS in it's latest version. 
> 
> 
> The idea behind all that was to grant 5 or six critical servers access to the NAS so that they can take advantage of : 
> 
> 1. space available on the NAS
> 
> 2. ability of the NAS to use ZFS and of clients to support this file system (including snapshots) 
> 
> 3. Access the server using iSCSI (at least this is what I initially planned). 
> 
> 4. Mount part of their filesystem using data stored on the SAN (like /usr/local/ or other parts of the system). 
> 
> 
> 
> The server accessing the data will be of two types : 
> 
> 1. 2 x Ubuntu server 10.04 LTS 
> 
> 2. 4 x FreeBSD (mainly 8 and 9) with jail configured 
> 
> 
> I have started reading about iSCSI and potential problems with FreeBSD. 
> 

What problems do you mean ?



> So my main questions would be : 
> 
> 
> • Should I go for iSCSI ? 
> 

Well in all use cases, iscsi should perform faster than NFS.



> • Should I rather choose / prefer NFS ? 
> 
> • Should I export a Volume as UFS rather than ZFS (is ZFS supported as a target) ?
> 

I'm not sure what you mean here, when you export a zvol over ISCSI:
- your SAN is the target and presents a block device (the zvol)
- your client is the initiator
- your client attaches to the ISCSI drive and formats it using filesystem XYZ, be it ext3, ufs or ntfs




> 
> The main idea is stability, redundancy of data and ease of maintenance (in a headless FreeBSD / Linux world) before anything else ! 
> 

ISCSI is a bit harder to setup IMO, however I think it''s more reliable than NFS, what with its auto retries if it loses the network link to a device.



> 
> 
> That's the big pictures, if you have any pointers, advise, they are all welcome. 
> 
> 
> It is quite late where I leave, so I will reply to posts in 8 to 10 hours, but I hope to have enough answer(s) to start an interesting thread (as I think this question is very interesting and not so clearly explained (at least in my mind))… 
> 

This is idd a very interesting topic and I hope to see more :)



> 
> Thx very much for your infos and feedback.