If you are worried about wearing out the SSD's long term get a larger SSD and
create the partition smaller than the disk, this will reduce the write
amplification and extend the life of the drive.
TRIM support also helps lower write amplification issues by not requiring as
many pages to do the writes, and improve performance as well!
As a test I bought 4 cheap 40GB drives in a raid0 software stripe, I have run
it for almost a year now with a lot of random IO. I portioned them as 30GB
drives, leaving an extra 25% spare area to reduce the write amplification, I
can still get over 600MB/sec on these for a whopping cost of $400 and a little
of my time.
SSD's can be very useful, but you have to be aware of the shortcomings and how
to overcome them.
- John
-Original Message-
From: Marti Raudsepp [mailto:ma...@juffo.org]
Sent: Thursday, December 09, 2010 6:09 AM
To: Scott Marlowe
Cc: Benjamin Krajmalnik; John W Strange; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Hardware recommendations
On Thu, Dec 9, 2010 at 04:28, Scott Marlowe scott.marl...@gmail.com wrote:
On Wed, Dec 8, 2010 at 5:03 PM, Benjamin Krajmalnik k...@servoyant.com
wrote:
My biggest concern with SSD drives is their life expectancy,
Generally that's not a big issue, especially as the SSDs get larger.
Being able to survive a power loss without corruption is more of an
issue, so if you go SSD get ones with a supercapacitor that can write
out the data before power down.
I agree with Benjamin here. Even if you put multiple SSD drives into a
RAID array, all the drives get approximately the same write load and
thus will likely wear out and fail at the same time!
As for the Areca controllers, I haven't tested them with the latest
drivers or firmware, but we would routinely get 180 to 460 days of
uptime between lockups
That sucks! But does a BBU even help with SSDs? The flash eraseblock
is larger than the RAID cache unit size anyway, so as far as I can
tell, it might not save you in the case of a power loss.
Any thoughts whether software RAID on SSD is a good idea?
Regards,
Marti
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