[OpenIndiana-discuss] SSDs for ZFS Pool?

[Bryan N Iotti]

Sorry to reopen an old post, but I have some questions I can't seem to 
find an answer to myself...

I recently caved in and bought an LSI 3041E-R HBA, which I reflashed to 
Initiator Target firmware, the latest version available. I have my usual 
two 2TB SATA drives attached directly via SATA. I have encountered 
Illumos bug #1787 as described here:
https://www.illumos.org/issues/1787

Would installing a SAS-To-SATA interposer card on each disk clear this 
error, or would it still act the same way? I mean, if I understand 
right, this bug affect only SATA drives on SAS controllers.

Should I just cave in once more and buy some SAS disks, if SMART is so 
important to me?


Any thoughts welcome.

Bryan

On 08/20/12 05:08 PM, Sašo Kiselkov wrote:
> On 08/20/2012 04:55 PM, Sebastian Gabler wrote:
>> Hi,
>> Questions:
>>
>> - I understand that TRIM will not work in any stripe set, be it parity
>> based or not, correct?
> Correct, Illumos has no TRIM support (yet).
>
>> - will heavy writes (such as transferring data from dumps, which will
>> happen relatively often) lead to contention?
> That's more a question of the quality of SATA drives you plan to
> purchase. Read
> http://gdamore.blogspot.com/2010/08/why-sas-sata-is-not-such-great-idea.html
> for why SATA in a SAS environment isn't such a great idea. If you have
> to use SATA, I recommend getting SAS interposers for them, e.g.
> http://dataonstorage.com/dataon-products/6g-sas-to-sata-interposer-card-and-kit.html
> (for example all SATA drives shipped in Sun JBODs had interposers)
>
>> - Should I upgrade the HBAs to something newer like LSI2008, for
>> compatibility reasons (no, I probably don't need the extra bandwidth SAS
>> 6g offers!)
> The LSI SAS1068 are very high quality chips, so if you feel you don't
> need 6G SAS, there's probably no need to upgrade. LSI SAS2008, however,
> can be had at extremely competitive prices (<100USD for a new
> Dell-branded external HBA card with the chips is an extremely attractive
> proposition) and are also very stable.
>
>> - Are there any SSDs that you could recommend?
> OCZ Talos R, though these are quite pricey. You might want to look into
> stuffing it with normal 7k2 rpm drives and getting a suitably-large
> L2ARC device (these can do wonders, my crappy little 60GB Vertex 3 can
> push >90MB/s and >10k iops in 8k random reads).
>
>> - with some desktop HDs, I experienced that they will be kicked out of
>> the array for no obvious reason - does that happen with consumer SSDs as
>> well, i.e. while the controller re-balances free cells for writing?
> It's more a problem of the SATA circuitry which can't cope with the
> constant battery of commands when your pool is taking a bad beating. See
> above for my opinion on SATA vs. SAS.
>
>> - should I better use 10 K SAS drives w/ flash-based ZIL?
> Drive speed isn't all that important if you get a suitably large L2ARC.
> If your databases are going to be used for testing only (so data loss in
> case the machine goes down isn't that big an issue), you might want to
> turn the ZIL entirely off. It's quite a performance killer unless you
> choose to dump a bunch of money into an expensive slog device (e.g.
> ddrdrive, zeusram, etc.).
>
> --
> Saso
>
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