ZFS melting under postgres...

[Ivan Voras]

David Duchscher wrote:
> On Dec 14, 2007, at 6:57 AM, Dag-Erling Smørgrav wrote:
> 
>> David Duchscher <daved at 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.

It would be logical to use a limited size SSD for something like a file
system journal for a large file system, except that these kind of
journals are usually not seek-intensive :)

> Fastest ones I found have a top rating of 45MB/s.  The one
> battery backed NVARM card that showed up in a google search had a peak
> rate of 533MB/s.  The question seems moot though since FreeBSD doesn't
> currently support them.

If a NVRAM or SSD, or other technology presents the drive as a (S)ATA
drive, there's no reason it shouldn't.

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