Re: BBU still needed with SSD? - Mailing list pgsql-performance

From Yeb Havinga
Subject Re: BBU still needed with SSD?
Date
Msg-id 4E23E72B.2070508@gmail.com
Whole thread Raw
In response to BBU still needed with SSD?  (Andy <angelflow@yahoo.com>)
Responses Re: BBU still needed with SSD?  (Florian Weimer <fweimer@bfk.de>)
List pgsql-performance
On 2011-07-18 03:43, Andy wrote:
> Hi,
>
> Is BBU still needed with SSD?
>
> SSD has its own cache. And in certain models such as Intel 320 that cache is backed by capacitors. So in a sense that
cacheacts as a BBU that's backed by capacitors instead of batteries. 
>
> In this case is BBU still needed? If I put 2 SSD
+with supercap?
>   in software RAID 1, would that be any slower than 2 SSD in HW RAID 1 with BBU? What are the pros and cons?
The biggest drawback of 2 SSD's with supercap in hardware raid 1, is
that if they are both new and of the same model/firmware, they'd
probably reach the end of their write cycles at the same time, thereby
failing simultaneously. You'd have to start with two SSD's with
different remaining life left in the software raid setup.

regards,
Yeb



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