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Date: Fri, 14 Dec 2007 19:02:12 -0800
From: Maxim Sobolev <sobomax@FreeBSD.org>
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To: Ivan Voras <ivoras@FreeBSD.org>
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Cc: freebsd-current@FreeBSD.org
Subject: Re: ZFS melting under postgres...
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Ivan Voras wrote:
> David Duchscher wrote:
>> On Dec 14, 2007, at 6:57 AM, Dag-Erling Smørgrav wrote:
>>
>>> David Duchscher <daved@tamu.edu> writes:
>>>> So does anybody know of a battery backed NVRAM card that can be used
>>>> with FreeBSD that the ZIL could be offloaded to?
>>> Any CF card or similar will do.  You don't need battery backup for
>>> flash memory.
>> I did think of that but is a CF card faster than a good SAS or SATA
>> drive? 
> 
> Not in transfer rate, but it could help hugely with seek-intensive IO
> loads (since seeks are instantaneous on flash or other solid-state
> drives). In theory, they could be of immense benefit for databases and
> seek-intensive operations on file systems, but the limited bulk transfer
> rates and relatively small sizes (for decent money) currently prevent
> their wide-spread use.

That's no longer true. You can't get more than 5-10MB/s from 
seek-intensive RAID0 with two 15K drives, while 20-30MB/s is not a 
problem for the comparable priced/sized SSD drive.

-Maxim