Le 27 nov. 2012 à 01:17, Erik Trimble a écrit :

> On 11/26/2012 12:54 PM, Grégory Giannoni wrote:
>> [snip]
>> I switched few month ago from Sun X45x0 to HP things : My fast NAS are now 
>> DL 180 G6. I got better perfs using LSI 9240-8I rather than HP SmartArray 
>> (tried P410 & P812). I'm using only 600Gb SSD drives.
> That LSI controllers supports SATA III, or 6Gbps SATA.   The Px1x controllers 
> do 6GB SAS, but only 3GB SATA, so that's your likely perf difference.  The 
> SmartArray Px2x series should do both SATA and SAS at 6Gbps.

The SSD drives I'm using (Intel 320 600GB) are limited to 270MB/sec ; So I 
don't think that SATA II is limiting.

> That said, I do think you're right that the LSI controller is probably a 
> better fit for connections requiring a SATA SSD.  The only exception is 
> having to give up the 1GB of NVRAM on the HP controller. :-(

I don't think that this is a real issue when using a bunch of SSDs. I even 
wonder if the NVRAM is not slowing down writings. My tests were done with ZIL 
enabled, so a power loss shouldn't damage the datas.

>> [...]
> Is the bottleneck the LSI controller, or the SAS/SATA bus, or the PCI-E bus 
> itself?  That is, have you tested with LSI 9240-4i  (one per 8-drive cage, 
> which I *believe* can use the HP multi-lane cable), and with a LSI 9260-16i 
> or LSI 9280-24i?   My instinct would be to say it's the PCI-E bus, and you 
> could probably get away with the 4-channel cards.  i.e. 4-channels @ 6Gbit/s 
> = 3 GBytes/s > 4x PCI-E 2.0 at 2GB/s

The first bottleneck we reached (DL 180 / standard 25 drives bay) was the HP 
controller (both P410 AND P812 reached the same perfs : 800MB/sec writing, 
1.3GB/sec reading).

With LSI 9240-8I, we reached 1.2GB/s writing, 1.3Gb/s reading.

The LSI 9240-4I was not able to connect to the 25-drives bay ; Not tested  LSI 
9260-16I or LSI 9280-24i.

The results were the same with 10 or 25 drives, so I suspected either the PCI 
bus, either the expander in the 25-drives bay (HP 530946-001).
Plugging the disks directly to the LSI card allowed to gain few MB/s : the 
expander was limiting a bit, but moreover, it disallowed to use more than 1 
disk controller !

By replacing the 25-drives bay by three 8-drives bays (507803-B21), the system 
was able to use 3 LSI 9240-8I, with this 4.4GB/sec reading rate.

Grégory Giannoni
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