Areca vs. ZFS performance testing.

[Matt Simerson]

On Nov 17, 2008, at 3:43 AM, Danny Carroll wrote:

> Matt Simerson wrote:
>> Allow me to introduce you to Marvell. The sell the SATA controller  
>> used
>> in the Sun thumper (X4500). I've used that same SATA controller under
>> OpenSolaris and FreeBSD. Unfortunately, that controller doesn't use
>> multi-lane cables. When you pack in 3 controllers and 24 disks,  
>> it's a
>> cabling disaster.
>>
>>    http://freebsd.monkey.org/freebsd-fs/200808/msg00027.html
>
> Interesting.  Wish I had seen it before.  To be honest I did consider
> this board but I was really in favour of PCIe over PCIX.  That might
> have been a mistake :-)
>
>> The Areca cards do NOT have the cache enabled by default. I ordered  
>> the
>> optional battery and RAM upgrade for my collection of 1231ML cards.  
>> Even
>> with the BBWC, the cache is not enabled by default. I had to go out  
>> of
>> my way to enable it, on every single controller.
>
> Are you talking about the Areca cache or the disks own caches?

Disk caching is a completely different animal, and one which I didn't  
mention.  I'm spoke only about the write cache on the controller. Mine  
all arrived off by default, which is a VERY reasonable default  
configuration. Page 97 of the manual says about it:

>>> 3.7.5.12 Disk Write Cache Mode
>>> User can set the "Disk Write Cache Mode" to Auto, Enabled, or
>>> Disabled. Enabled increases speed, Disabled increases reliability.

> On my board it was enabled.  But maybe mine was the exception.

Perhaps it's model specific, or your vendor configured it that way. Or  
you got a return that someone else monkeyed with. I'm not going to  
speak for Areca but it seems quite odd that Areca would ship them with  
the cache enabled. I've used many hundreds of RAID controllers over  
the years and without exception, every single one with a write cache  
had it disabled by default.

Matt