Dell branded storage controller for ZFS file-server | Advice requested

[Ahmed Kamal]

Thanks a lot for your reply .. I've got a couple of questions inline

On Fri, Jan 23, 2015 at 12:21 PM, David Gwynne <david at gwynne.id.au> wrote:

>
> > On 23 Jan 2015, at 7:16 pm, Ahmed Kamal <email.ahmedkamal at googlemail.com>
> wrote:
> >
> > Hi everyone,
> >
> > I'm looking to build a ZFS file-server, unfortunately I'm locked into
> Dell
> > branded hardware only. I know Dell sometimes ships LSI branded cards, but
> > that too probably won't work for me, as I live outside the US and the
> local
> > Dell rep is clueless (so whatever I want to buy, has to be on Dell's
> > website). I am considering Dell R720xd or R730xd. I will use Intel i350
> > NICs, and ECC RAM, but the biggest questions are around the SAS HBA
> >
> > Per my research, I have the following notes and questions. Appreciating
> > your comments on them
> >
> > * H310 Card supports syspd (jbod) mode per
> > http://svnweb.freebsd.org/base?view=revision&revision=254906 so it is
> > probably the best card for what I want to do, right?
>
> no.
>
> > * H310 is a low end card, it has very limited queue depth (25 I believe)
> ..
> > Is this actually a problem when using the disks (20 x SAS 10k disks) in
> > syspd/jbod mode? what about if I attach a couple of SSD disks?
>
> there are two queue limits here, one for the controller and one for each
> disk attached to it.
>
> h310s have a controller queue depth of 31, ie, they can only support 31
> commands at a time. if you have 24 disks and distribute the controllers
> command slots between them, thats about 1 command per disk.
>

My initial line of thought was that in pass-through (jbod) mode, the HBA
does *not* buffer commands and proxy disk responses internally. Which meant
that in jbod mode, the HBA basically becomes a communications channel
connecting the OS to disks, making its internal buffering limitations
not-applicable. Is this not correct ?


>
> > * H310 can be flashed to IT mode (LSI firmware), and is supported by
> > Illumos kernel (if I'll ever need that) .. so overall it looks like a
> good
> > option. Any "watch-outs" I should be aware of ?
>
> yes. if you flash the h310 to become an sas hba, the pci product/vendor
> and subproduct/subvendor ids on the controller change. the dell bios will
> refuse to boot if it detects an unsupported controller in its storage slot.
> you'll brick the machine until you remove the h310. because it is on a non
> standard mezzanine connector you will not be able to flash it back to a
> h310, and you'll have a useless chunk of silicon to put on your desk as a
> monument to how annoying vendors are.
>

pff nightmare scenario .. thanks for pointing this out. I stumbled across
web posts where people successfully flashed h310, but meh, now I'm scared
to buy that configuration


>
> > * H710/p have no way of exposing JBOD/syspd in any way .. If using those
> > cards, the best I can do, is to create a raid-0 per disk, and put zfs on
> > top of that. How bad is this? Is the only problem that I'm locked into
> H710
> > firmware? Would the nvram and bbu on H710 improve performance
> significantly
> > vs H310?
>
> i wouldnt run zfs on that.
>
> > * H330 and H730, seem supported by mrsas driver. Is this driver able to
> > expose jbod/syspd mode? If yes, what's the overall advise, should I go
> with
> > one of those, or the "trusty" H310 ?
>
> thats a workable option. h330 should be fine if all you want to do is jbod.
>

Now that you're pointing me to H330 being my best option given the
situation, got some more questions:
* "if all you want is jbod" .. with zfs, that's all we need right ? just
wondering if I'm missing something important
* Any idea if jbod configuration on h330 is done on bios level, or using
some freebsd tool (how?)
* mrsas man page, mentions the driver appeared in 10.1 .. Does that mean if
I decide to use FreeNAS (9.x based) it won't be there ?
* If I go the h330 path, it'll be a r730xd server. Worst case if the h330
gives me trouble, can I throw it out and plug a LSI 9207-8i in its place
(same pci slot, cables ..etc) ?

Thanks!


>
> >
> > Your help and advice is most appreciated
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