Re: Do I have a hardware or a software problem?

On 12/12/2012 06:44 AM, Evgeny Shishkin wrote:
>
> On Dec 12, 2012, at 2:41 AM, Niels Kristian Schjødt
> <nielskristian(at)autouncle(dot)com <mailto:nielskristian(at)autouncle(dot)com>> wrote:
>
>> Are you using a hardware based raid controller with them?
>>
> Yes, of course. Hardware raid with cache and bbu is a must. You can't
> get fast fsync without it.

Most SSDs should offer fairly fast fsync without a hardware RAID
controller, as they do write-back caching. The trick is to find ones
that do write-back caching safely, so you don't get severe data
corruption on power-loss.

A HW RAID controller is an absolute must for rotating magnetic media,
though.

> Also mdadm is a pain in the ass and is suitable only on amazon and
> other cloud shit.

I've personally been pretty happy with mdadm. I find the array
portability it offers very useful, so I don't need to buy a second RAID
controller just in case my main controller dies and I need a compatible
one to get the array running again. If you don't need a BBU for safe
write-back caching then mdadm has advantages over hardware RAID.

I'll certainly use mdadm over onboard fakeraid solutions or low-end
hardware RAID controllers. I suspect a mid- to high end HW RAID unit
will generally win.

--
Craig Ringer http://www.2ndQuadrant.com/
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