SSD recommendations for ZFS cache/log

[Chris BeHanna]

On Nov 13, 2012, at 22:27 , Bryan Drewery <bryan at shatow.net> wrote:

> On 11/13/2012 10:18 PM, Chris BeHanna wrote:
>> On Nov 13, 2012, at 21:51, Stephen McKay <smckay at internode.on.net> wrote:
>> 
>>> [...lots of good advice about measuring, and lots of good advice about L2ARC...]
>>> 
>>> I have no way to determine in advance the behaviour of an SSD on
>>> power failure so I assume all the ones I can afford have bad
>>> behaviour. :-)  I know that expensive ones contain capacitors so
>>> that power failures do not corrupt their contents.  By the nature
>>> of advertising (from which we know that any feature not excessively
>>> hyped must therefore not be supported), we must conclude that other
>>> SSDs by normal operation corrupt blocks on power failure.
>> 
>> If you'll pardon what may be an ignorant question, does this matter if you have your machine on a UPS, especially if you run upsmon or nut to do a graceful shutdown when there are n minutes of battery remaining?
> 
> I've had more than 1 UPS battery die on me, resulting in instant shutoff.

	Mine always die at 0300 or thereabouts, and none of my UPSen has an "I know, now STFU" button.

	I would gather that the extra expense of a capacitor-backed SSD if you already have a UPS (with relatively new batteries) depends upon the particular use case.  Banking data?  Hell yeah.  Home office?  Meh.  I might lose a few pieces of spam and the last few minutes of work from my text editor.

-- 
Chris BeHanna
chris at behanna.org