Support for Fusion IO drives?

[Nikolay Denev]

Fron the zpool man page:

     By default, the intent log is allocated from blocks within the main pool.
     However, it might be possible to get better performance using separate
     intent log devices such as NVRAM or a dedicated disk.

I was also contemplating the idea of a fast SSD on PCIe as a ZIL and L2ARC.
And given the fact that the SSD will not suffer from the different types and locations of IO requests,
maybe it makes sense to go with a big SSD, and partition it for a small ZIL partition,
and the rest for L2ARC. Anyone tried that?

Regards,
Nikolay

On Aug 29, 2012, at 2:47 AM, Andrew Young <ayoung at mosaicarchive.com> wrote:

> Thanks for the great feedback Josh! The optimum size for an ssd zil device was still an open question for us. I'm really glad to hear that they don't need to be that big.
> 
> What does zfs do with the zil if there is no dedicated zil device? Our servers consist of a small sata drive that holds the OS and a boatload of larger drives on a sas bus. What I'm wondering is if I simply replace the OS disk with an ssd will I get the same performance boost as if I added a dedicated ssd zil? 
> 
> Thanks!
> Andy
> 
> On Aug 28, 2012, at 7:07 PM, Josh Paetzel <josh at tcbug.org> wrote:
> 
>>>> -------- Original Message --------
>>>> Subject: Support for Fusion IO drives?
>>>> Date: Tue, 28 Aug 2012 16:46:00 -0400
>>>> From: Andy Young <ayoung at mosaicarchive.com>
>>>> To: freebsd-hardware at freebsd.org
>>>> 
>>>> 
>>>> We are investigating adding SSDs as ZIL devices to boost our ZFS write
>>>> performance. I read an article a while ago about iX Systems teaming up
>>>> with
>>>> Fusion IO to integrate their hardware with FreeBSD. Does anyone know
>>>> anything about supported drivers for Fusion IO's iodrives?
>>>> 
>>>> Thanks!
>>>> 
>>>> Andy
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>>>> 
>>>> 
>>>> 
>> 
>> I'll put on my iXsystems hat here, as well as my fast storage, ZFS and
>> Fusion-I/O hat.
>> 
>> The ZFS filesystem supports dedicated ZIL devices, which can accelerate
>> certain types of write requests, notably related to fsync.  The VMWare
>> NFS client issues a sync with every write, and most databases do as
>> well.  In those types of environments having a fast dedicated ZIL device
>> is almost essential.  In other environments the benefits of a dedicated
>> ZIL range from non-existent to substantial.
>> 
>> A good dedicated ZIL device is all about latency.  It doesn't need to be
>> large, in fact it will only ever handle 10 seconds of writes, so 10x
>> network bandwidth is worst case. (In most environments this means 20GB
>> is larger than needed).
>> 
>> Fusion-I/O cards are far too large to be cost effective ZIL devices.
>> Even though they do rock at I/O latency, the really fast ones are also
>> fairly large, so the $/GB on them isn't so attractive.  There are better
>> options for ZIL devices.
>> 
>> Another consideration is the Fusion-I/O driver is fairly memory hungry,
>> which competes with memory ZFS wants to use for read caching.
>> 
>> Now as an L2ARC device, that's a whole different can of worms.
>> 
>> Command line used: iozone -r 4k -s 96g -i 0 -i 1 -i 2 -t 8
>> Parent sees throughput for  8 readers           = 1712399.95 KB/sec
>> L2 ARC Breakdown:                               197.45m
>> Hit Ratio:                      98.61%  194.71m
>> L2 ARC Size: (Adaptive)                         771.13  GiB
>> ARC Efficiency:                                 683.40m
>> Actual Hit Ratio:               71.09%  485.82m
>> 
>> ~ 800GB test data, all served from cache.
>> 
>> If you are considering Fusion-I/O, the FreeBSD driver is generally not
>> released to the general public by Fusion-I/O, but can be obtained from
>> various partners. (I believe iXsystems is the only FreeBSD friendly
>> fusion-i/o partner but could be wrong about that)
>> 
>> 
>> -- 
>> Thanks,
>> 
>> Josh Paetzel
>> 
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