Message-ID: <50B93678.3090100@catalyst.net.nz>
Date: Sat, 01 Dec 2012 11:43:04 +1300
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
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To: Vitalii Tymchyshyn <tivv00@gmail.com>
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Subject: Re: Optimize update query
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Hmm - not strictly true as stated: 1 SSD will typically do 500MB/s 
sequential read/write. 1 HDD will be lucky to get a 1/3 that.

We are looking at replacing 4 to 6 disk RAID10 arrays of HDD with a 
RAID1 pair of SSD, as they perform about the same for sequential work 
and vastly better at random. Plus they only use 2x 2.5" slots (or, ahem 
2x PCIe sockets), so allow smaller form factor servers and save on power 
and cooling.

Cheers

Mark

On 30/11/12 23:07, Vitalii Tymchyshyn wrote:
> Oh, yes. I don't imagine DB server without RAID+BBU :)
> When there is no BBU, SSD can be handy.
> But you know, SSD is worse in linear read/write than HDD.
>
> Best regards, Vitalii Tymchyshyn
>
>
> 2012/11/30 Mark Kirkwood <mark.kirkwood@catalyst.net.nz
> <mailto:mark.kirkwood@catalyst.net.nz>>
>
>     Most modern SSD are much faster for fsync type operations than a
>     spinning disk - similar performance to spinning disk + writeback
>     raid controller + battery.
>
>     However as you mention, they are great at random IO too, so Niels,
>     it might be worth putting your postgres logs *and* data on the SSDs
>     and retesting.
>


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