Re: BBU still needed with SSD?

On 18/07/2011 9:43 AM, Andy wrote:
> Hi,
>
> Is BBU still needed with SSD?
You *need* an SSD with a supercapacitor or on-board battery backup for
its cache. Otherwise you *will* lose data.

Consumer SSDs are like a hard disk attached to a RAID controller with
write-back caching enabled and no BBU. In other words: designed to eat
your data.

> In this case is BBU still needed? If I put 2 SSD in software RAID 1, would that be any slower than 2 SSD in HW RAID 1
withBBU? What are the pros and cons? 
>
You don't need write-back caching for fsync() performance if your SSDs
have big enough caches. I don't know enough to say whether there are
other benefits to having them on a BBU HW raid controller or whether SW
RAID is fine.

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