Re: Compression of full-page-writes - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: Compression of full-page-writes
Date
Msg-id CAM3SWZSWV7km5AMqtDMXOA8vWnfrCTX2XA6fr5wwnW2PTQLw0Q@mail.gmail.com
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In response to Re: Compression of full-page-writes  (Fujii Masao <masao.fujii@gmail.com>)
List pgsql-hackers
On Thu, Aug 29, 2013 at 10:55 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
>> I suppose that the cost of the random I/O involved would
>> probably dominate just as with compress_backup_block = off. That said,
>> you've used an SSD here, so perhaps not.
>
> Oh, maybe my description was confusing. full_page_writes was enabled
> while running the benchmark even if compress_backup_block = off.
> I've not merged those two parameters yet. So even in
> compress_backup_block = off, random I/O would not be increased in recovery.

I understood it that way. I just meant that it could be that the
random I/O was so expensive that the additional cost of decompressing
the FPIs looked insignificant in comparison. If that was the case, the
increase in recovery time would be modest.

-- 
Peter Geoghegan



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