ZFS + iSCSI architecture

[bsd at todoo.biz]

Le 20 févr. 2013 à 02:14, Fleuriot Damien <ml at my.gd> a écrit :

> 
> 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 ?

For example : 

- Can my client (the initiator) directly mount a ZFS volume on freeBSD using iSCSI or should I go back to formatting It to UFS ?

- Is the iSCSI stack in FreeBSD stable an mature enough to be used in a production environment ?
==> It is out of scope to have kernel panic because of an unstable iSCSI related problem. 


> 
>> So my main questions would be : 
>> 
>> 
>> • Should I go for iSCSI ? 
>> 
> 
> Well in all use cases, iscsi should perform faster than NFS.

Fast is good - stable is necessary in this case ! 
And this is what I am tring to evaluate… 

> 
>> • 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
> 

Thanks for this reminder about vocabulary for iSCSI, I'll try to stick to It ;-) 

> 
>> 
>> 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.
> 

Have you deployed this in production and what are your concerns and recommendations ? 

> 
> 
>> 
>> 
>> 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 :)
> 

There is also an interesting (and fresh) post here : 

http://utcc.utoronto.ca/~cks/space/blog/solaris/ZFSFreeBSDvsIllumos?showcomments#comments

> 
>> 
>> Thx very much for your infos and feedback. 
> 
> 

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