| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Smith <greg(at)2ndQuadrant(dot)com> |
| Cc: | Hannu Krosing <hannu(at)2ndQuadrant(dot)com>, didier <did447(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Design proposal: fsync absorb linear slider |
| Date: | 2013-07-26 12:32:01 |
| Message-ID: | 13245.1374841921@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Greg Smith <greg(at)2ndQuadrant(dot)com> writes:
> On 7/26/13 5:59 AM, Hannu Krosing wrote:
>> Well, SSD disks do it in the way proposed by didier (AFAIK), by putting
>> "random"
>> fs pages on one large disk page and having an extra index layer for
>> resolving
>> random-to-sequential ordering.
> If your solution to avoiding random writes now is to do sequential ones
> into a buffer, you'll pay for it by having more expensive random reads
> later.
What I'd point out is that that is exactly what WAL does for us, ie
convert a bunch of random writes into sequential writes. But sooner or
later you have to put the data where it belongs.
regards, tom lane
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