[Dovecot] Indexes to MLC-SSD

[Dovecot-GDH]

If I/O performance is a concern, you may be interested in ZFS and Flashcache.

Specifically, ZFS' ZIL (ZFS Intent Log) and its L2ARC (Layer 2 Adaptive Read Cache)
ZFS does run on Linux http://zfs-fuse.net

Flashcache: https://github.com/facebook/flashcache/

Both of these techniques can use a pair of SSDs in RAID1 rather than a single SSD.

On Oct 27, 2011, at 1:31 AM, Ed W wrote:

> On 27/10/2011 03:36, Stan Hoeppner wrote:
>> On 10/26/2011 4:13 PM, Patrick Westenberg wrote:
>>> Hi all,
>>> 
>>> is anyone on this list who dares/dared to store his index files on a
>>> MLC-SSD?
>> I have not.  But I can tell you that a 32GB Corsair MLC SSD in my
>> workstation died after 4 months of laughably light duty.  It had nothing
>> to do with cell life but low product quality.  This was my first foray
>> into SSD.  The RMA replacement is still kickin after 2 months,
>> thankfully.  I'm holding my breath...
>> 
>> Scanning the reviews on Newegg shows early MLC SSD failures across most
>> brands, early being a year or less.  Some models/sizes are worse than
>> others.  OCZ has a good reputation overall, but reviews show some of
>> their models to be grenades.
>> 
>> Thus, if you were to put indexes on SSD, you should strongly consider
>> using a mirrored pair.
>> 
> 
> I don't think you are saying that the advice varies here compared with
> HDDs?  I do agree that some SSDs are showing very early failures, but
> it's only a tweak to the probability parameter compared with any other
> storage medium.  They ALL fail at some point, and generally well within
> the life of the rest of the server.  Some kind of failure planning is
> necessary
> 
> Caveat the potentially higher failures vs HDDs I don't see any reason
> why an SSD shouldn't work well? (even more so if you are using maildir
> where indexes can be regenerated).
> 
> More interestingly: for small sizes like 32GB, has anyone played with
> the "compressed ram with backing store" thing in newer kernels (that I
> forget the name of now). I think it's been marketed for swap files, but
> assuming I got the theory it could be used as a ram drive with slow
> writeback to permanent storage?
> 
> Good luck
> 
> Ed W