Suggested best Zil and L2arc drives? Revodrive3 vs Vertex 3

P

piece3

Hello,

I'm currently purchasing the hardware to build a zfs san, I'm now trying to decide on the current best drives for the zil and the l2arc. I see that MLC is now ok to use as the ZIL where a year ago it had to be SLC.

What is the best drive to use for a ZIL?

Has anybody succesfully used OCZ's revodrive 3 or velodrive 3?

I haven't been able to find the vertex3 pro with the supposed capacitor as per this post http://forums.freebsd.org/archive/index.php/t-23566.html. Is it available?

Do you still need to mirror the Velodrive 3 (as that would be expensive, and seems a large capacity for a ZIL)

Is OCZ the only company worth considering or are there others that produce suitable ZIL's?

Thanks very much for your help
 
Search through the zfs-discuss mailing list archives. This topic comes up at least twice a year on that list. :) And there's many, many, many advanced/enterprise users of ZFS on there.

MLC/SLC doesn't really matter anymore. The most important things for a ZIL drive are that when the drive says "sync complete" the data is actually on the disk; and that if the drive loses power, there's a way for it to write out all data in the cache to the disk (whether that be a separate PSU, a BBU, a super-cap, etc).

If money is no object, Fusion-IO PCIe cards are the best hardware for a ZIL. ;)
 
@piece3

Hey man,

it is super-cool to see you've read my tests. I started those because I noticed there was alot of writings about ZIL, but all of it was theoretical and no real-world tests, and benchmarks done was to test just about everything except how good of a SLOG the drives would make. Firstly a disclaimer though. I was a complete noob when I started that thread, but I got wiser as time went by. I still can't say I know everything now, just better than when I started:) And I have been completly open about how my test were made and no one has yet to argue my methods, so I'd say I've done OK so far. Still I encourage you to test all of this yourself, so that we can compare our results.

I searched about revo/velodrives regarding super capacitor. Velodrive R-series are good to use. Tricky part was that it was hard to differentiate between which series Velodrive had it. C-series has no capacitor.
Examples:
R-series: VD-HHPX8-300G = good
C-series: VDC-HHPX8-320G = bad

About the Vertex 3 Pro, I would like to know that myself, I've been looking and looking come up zilch so far. Best guess is that it is now known as Deneva, sold through OCZ's corporate section at:
http://www.oczenterprise.com/
The specs are the same if you compare Deneva with Vertex 3 of equal size.

Mirroring is unnecessary from 8.2-STABLE and up.

I have had all companies in mind when doing my tests. For example, I've had the chance to test the Zeus IOPS, which are rare, only beeing sold b2b, strictly enterprise. But from reading most benchmarks on SSD's, I've noticed which where best and tested them accordingly. If e.g. Corsair were to score top on some benchmark sites tomorrow, of course I'd want to test it out. Thing is, Corsair and OCZ uses much of the same hard- and firmware so their scores are usually about the same, so it's then a question of capacitor and price instead. Also, as phoenix said, Fusion-IO, said to be the best but are untested by myself since they are waaay out of my price-league:) Also they cannot be used in a HA-cluster, because of it's PCI-e form factor, while disks in a JBOD can be shifted from one head to another. Same goes for the Velodrive.

/Sebulon
 
Thank you Phoenix and Sebulon for the helpful info,

The Fusion-IO PCIe cards look great, however they would blow the budget for the ZFS we're planning on building.

Considering the cost and performance of the OCZ options, the Deneva 2 SLC 30GB looks suitable for a ZIL. The Talos 230GB MLC SAS would have been nice owing to the fact that it's SAS and can connect to 2 controllers for redundancy, however 230GB is overkill for a ZIL. Good to see with the new version of the OS that if a ZIL drive fails, then it just reverts to saving the data to a standard disk therefore eliminating the need to mirror the ZIL, this would also indicate that having a capacitor onboard the ZIL device is no longer a requirement.

Is using an SLC device over a new MLC type device advantages? The 30GB Deneva 2 SLC is around USD$230, so is quite cheap for a ZIL.

I was unable to find "Sync Complete" anywhere on the OCZ datasheet for the Deneva 2, so not sure if it has a cap or not.

I'm still unsure of what to use for an L2ARC, I'm favouring the OCZ Deneva 2 MLC 120GB drive at the moment.
 
@piece3

Understand that the performance of the drive is directly linked to it´s size, because of the internal RAID0 that is used in SSD´s. The bigger they are, the faster. The Vertex 3 I benchmarked is the 240GB model, not 30GB! I´ve made that mistake myself and became very disappointed to learn the difference in performance. You will need a Deneva MLC of equal size to expect the same performance. I know the size is overkill, but trust me, you´ll deeply regret it otherwise.

About Deneva´s capacitors:
http://www.hardwarenew.net/ocz-deneva-ssd-review
Furthermore, the Deneva 2 capacitors on board who ensure that all data can be safely written to the loss of power, a feature which is desirable especially in professional applications.
Click to expand...

For L2ARC, the Vertex 3 240GB has been very satisfactory for me personally. I´m currently using it in a server that replaces a retired Sun/Oracle Unified Storage System 7310.
Heads up about that, is that it is important to know that ZFS still needs RAM to be able to allocate L2ARC. Very roughly explained is that if you have 10GB of RAM, you can allocate about 100GB of L2ARC. Just be mindful of the fact that you mustn´t forget about the RAM, just because you have L2ARC, is all.

/Sebulon
 
Thanks Sebulon,

The link for the capacitor info regarding Deneva 2's was very helpful.

The Cost of the 240GB MLC Deneva is around $330 compared with $360 for the 30GB SLC, so what your saying is the 240GB MLC will deliver better performance than the 30GB SLC?

I will be happy to use the 240GB Vertex 3 for the L2ARC. I'm currently using 16GB of ram in the system and 1 AMD 6128 CPU (though the motherboard has room to facilitate another).
 
...so what your saying is the 240GB MLC will deliver better performance than the 30GB SLC?
Click to expand...

That is impossible for me to answer, since I haven´t tested the Deneva 2 30GB SLC personally. I have however tested the Vertex 3 240GB and since it is identical (except for the capacitor) to the Deneva 2 240GB MLC, I can guarantee that performance.
But if you´re feeling adventurous you can buy the Deneva 2 30GB SLC, test it with the same MO as me, post back your results and I can then add it to my highscore:) Come to think of it, I would suggest you benchmark it and post back the results regardless of what which disk you decide to buy. It would be phenomenal to have stated for the record.
My best guess is that the Deneva 2 30GB SLC will have about the same score as the 32GB Intel X25-E.

If I'm to use the Deneva 2 MLC for a ZIL, would Async or Sync be better?
Click to expand...
If you´re doing it async, you´re not using the ZIL at all. Sync is what you want.

/Sebulon
 
Oh, I just realized I misunderstood you. You were referring to OCZ´s website on Deneva 2. It says "2.5" Deneva 2 (Sync)" vs. "2.5" Deneva 2 (Async)". I have no idea what that is about. It there any difference in price?

BTW, 330$ for the worlds best ZIL device? Think you could score me one too?:)

/Sebulon
 
Ok Sebulon, I actually had the wrong price for the Deneva 2, it ended up costing $632. I also went for a Talos 230GB which will initially be used for the L2ARC. Once benchmarking has been completed for the current config, I might change them around and benchmark again. It's going to be a while though, the parts just arrived a few weeks ago, I'm in another country for the foreseeable future and have someone else not familiar with SAN's building and installing the system. I'll post benchmark figures once complete.
 
I searched about revo/velodrives regarding super capacitor. Velodrive R-series are good to use. Tricky part was that it was hard to differentiate between which series Velodrive had it. C-series has no capacitor.
Click to expand...

I remembered my own words trying to figure out which model of the Deneva 2 that had a super-capacitor. The above still applies:

R-series: D2RSTK251M11-0200 = Good
C-series: D2CSTK251M14-0240 = Bad

Source:
Deneva 2 R Series Solid State Drives - 2.5" MLC
260u635.jpg


/Sebulon
 
@tingo

I may be completly wrong about this, but I have read here on this forum about driver support for one of those, and I´m not sure which one, or if it was both. And if I remember correctly it was using the siis(4) driver... It´s not easy being technical and senile at the same time;) But I think that´s how it was.

You can search the forum for "velodrive" or "revodrive" and also ask "@mav", since he´s the one who wrote the driver.

/Sebulon
 
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