zfs discuss - Nov 2010 - Any opinoins on these SSD''s?

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I''m shopping for an SSD for a ZIL.

Looking around on NewEgg, at the claimed (not sure I beleive them)
IOPS, these caught my attention:


Corsair Force         80GB   CSSD-F80GBP2-BRKT    50K 4K aligned ran.
write IOPS
OCZ Vertex 2         120GB   OCZSSD3-2VTX120G     50K 4K aligned ran.
write IOPS
A-DATA S559          128GB   AS599S0128GM         50K 4k aligned write
IOPS
Crucial RealSSD C300 128GB   CTFDDAC128MAG-1G1CCA 60K/30K 4k
read/write IOPS

Any opinions? stories? other models I missed?

Other questions:

1) The ZIL will be small compared to the size of these, can I use the
rest as L2ARC or is that not such a good idea?

2) Will ZFS align the ZIL writes in such a way that those IOPS numbers
will be close to attainable?

 -Kyle




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> Any opinions? stories? other models I missed?
I was a speaker at the recent OpenStorage Summit,
my presentation "ZIL Accelerator: DRAM or Flash?"
might be of interest:

http://www.ddrdrive.com/zil_accelerator.pdf

Best regards,

Christopher George
Founder/CTO
www.ddrdrive.com
-- 
This message posted from opensolaris.org

On Nov 11, 2010, at 15:08, Kyle McDonald wrote:
> Any opinions? stories? other models I missed?
>
> Other questions:
>
> 1) The ZIL will be small compared to the size of these, can I use  
> the rest as L2ARC or is that not such a good idea?
>
> 2) Will ZFS align the ZIL writes in such a way that those IOPS  
> numbers will be close to attainable?
All the models listed are seem to be based on the Sandforce SF-1200.  
There was some discussion on Sandforce''s technology on the list a  
little while back, and to me the general consensus was that there were  
concerns about how caching was done and what would occur if the power  
was suddenly disconnected:

http://mail.opensolaris.org/pipermail/zfs-discuss/2010-May/thread.html#41326
http://mail.opensolaris.org/pipermail/zfs-discuss/2010-May/thread.html#41588
http://mail.opensolaris.org/pipermail/zfs-discuss/2010-June/thread.html#42298

Since you were looking at NewEgg, you may want to look at the OCZ  
Vertex 2 Pro:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820227534

It''s based on the SF-1500 chip set, has a supercap in case the power  
goes out, and ECC of some kind (perhaps for the DRAM cache?). You''re  
getting less storage for the dollar, but it should still be more than  
sufficient for a "slog" device, and be more resilient.

To answer your questions:
1. Yes, that is technically possible. What''s "best" is
probably
determined by benchmarking / testing things out with the workload  
you''re expecting to have.
2. It could: depends on the partition is properly aligned and/or  
whether the disk itself can be queried for sector size (and if it lies  
about it).

For (2), see:
a. PSARC/2008/769: Multiple disk sector size support
	http://arc.opensolaris.org/caselog/PSARC/2008/769/
b. PSARC/2010/296: Add tunable to control RMW for Flash Devices
	http://arc.opensolaris.org/caselog/PSARC/2010/296/

(a) appears to have been fixed in snv_118 or so:

	http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6710930

Not sure if ZFS takes advantage of this information, or it it''s only  
the lower-level I/O code.

Also ran across the "ashift" property of zpools:

http://tinyurl.com/25gmy7o
http://www.solarismen.de/archives/5-Solaris-and-the-new-4K-Sector-Disks-e.g.-WDxxEARS-Part-2.html

There''s been quite some discussion on the topic over the last little  
while:

http://www.google.com/search?q=zfs+4k+sectors