[Gllug] Battery-backed SAS controllers

[James Courtier-Dutton]

2009/12/12 Andy Smith <andy at strugglers.net>:
> On Fri, Dec 11, 2009 at 06:34:08PM +0000, Andy Smith wrote:
>> Anyone know of a battery-backed SAS controller?  That is, something
>> like a RAID controller that takes SAS disks but without any RAID
>> features, just a battery backed write cache and the disks exposed to
>> the OS.
>
> Based on some off-list chatter maybe I could do with elaborating.
>
> I can remove the need for hardware RAID cards in all respects except
> their battery-backed write cache.
>
> By using a hardware RAID card I risk the hardware failing and taking
> all data with it.  Even holding spares of the card does not always
> protect against this.  It would be desirable to remove this point of
> failure.
>
> The cheapest 3ware SAS card with a BBU seems to be about £300, and
> it seems a shame to spend that only to put it in JBOD mode (which
> may not even use the BBU).
>
> I can turn on the write caches in the disks themselves, but they
> aren't battery-backed, so a power cut or some forms of kernel panic
> may well lead to data loss.
>
> I'm surprised something like this does not exist.
>

What architecture are you using? Your requirement is very rare which
is why it is not widely used.
The battery is still a single point of failure.

Something like DRDB might suit you better.
It helps by having redundant HDs as well as redundant controllers and
motherboards.
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