[OpenIndiana-discuss] SSDs for ZFS Pool?

[Jason Matthews]

I have several hundred SSDs in use as L2ARC. I have the monitoring system
querying SMART data a number of times per day looking at the percentage of
rated life used in effort to replace disks before we burn out the cells.

Each time this query runs, it dirties the logs with some messages in regards
to this error but it doesn't actually cause me any grief. I don't believe
this causes any data corruption issues and SMART still works.

My recommendation is to ignore the messages for now and worry about real
problems. 


j.

-----Original Message-----
From: Bryan N Iotti [mailto:ironsides.medvet at gmail.com] 
Sent: Friday, August 24, 2012 8:53 AM
To: Discussion list for OpenIndiana
Subject: Re: [OpenIndiana-discuss] SSDs for ZFS Pool?

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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