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On 12/19/2010 1:22 PM, Luke S Crawford wrote:
> 
> So, in the past I have been very anti-hardware raid, mostly because
> the cards I could afford wanted to charge me what another 3 spindles
> would cost, and usually had only 64MiB of battery-backed cache.
> Last time I benchmarked one of those cards, they were largely 
> indistinguishable, performance wise and reliability wise from linux
> md (at the time I was testing the 'half failed' mode that so many
> consumer sata drives fall into.  Both the hardware raid I tested
> (an expensive 3ware) and md dealt poorly with the half-failed drive.
> I solved the problem by simply moving to 'enterprise' sata, and 
> settled on linux MD and raid 1+0, because I saw no benefit to 
> paying for the raid card.)
> 
> Anyhow, I'm hearing things about new servers from dell and HP coming
> with RAID cards that have on the order of 1GiB of cache;  and better,
> it's flash-based cache, so no battery modules to pay for/worry about.
> 
> With that kind of cache, it seems to me like it may be time to 
> re-evaluate my prejudices;  with enough persistent write cache,
> raid5 can actually give better performance, from what I understand,
> than the raid 1+0 I use, given the same number of spindles, but 
> that cache is pretty important.  
> 
> Anyhow, I was wondering what experiences others have had with this?
> I mean, I'll have to start building larger boxes, I imagine, to
> justify the cost of the card (my current systems are 8 core, 
> 32GiB ram 4 disk systems;  it probably makes sense for me to
> double or triple that, which is pretty easily doable.) 
> 
> What I'm wondering, though, is what success other people have had with
> these cards, and with what Linux kernels?
> 

Dell's PERC H700 and H800 cards support (but don't require) NVRAM cache.
LSI makes the silicon for the cards but I don't know that you can buy
them direct. We've only had them for a few months but we've had no
problems so far.

- -- 
- -- Skylar Thompson ([email protected])
- -- http://www.cs.earlham.edu/~skylar/
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