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:marti@xxxxxxxxx] Sent: Thursday, December 09, 2010 6:09 AM To: Scott Marlowe Cc: Benjamin Krajmalnik; John W Strange; pgsql-performance@xxxxxxxxxxxxxx Subject: Re: Hardware recommendations On Thu, Dec 9, 2010 at 04:28, Scott Marlowe <scott.marlowe@xxxxxxxxx> wrote: > On Wed, Dec 8, 2010 at 5:03 PM, Benjamin Krajmalnik <kraj@xxxxxxxxxxxxx> 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 This communication is for informational purposes only. It is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction. All market prices, data and other information are not warranted as to completeness or accuracy and are subject to change without notice. Any comments or statements made herein do not necessarily reflect those of JPMorgan Chase & Co., its subsidiaries and affiliates. This transmission may contain information that is privileged, confidential, legally privileged, and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. Although this transmission and any attachments are believed to be free of any virus or other defect that might affect any computer system into which it is received and opened, it is the responsibility of the recipient to ensure that it is virus free and no responsibility is accepted by JPMorgan Chase & Co., its subsidiaries and affiliates, as applicable, for any loss or damage arising in any way from its use. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format. Thank you. Please refer to http://www.jpmorgan.com/pages/disclosures for disclosures relating to European legal entities. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
