Re: [Moosefs-users] SSDs

[Quenten G. <QG...@on...>]

Hi Steve

I'm also in the middle of building a simular configuration. 

Did you happen to consider using maybe FreeBSD with ZFS and a couple of smallish SSD for logs? After thinking about it this morning I imagine this could considerably lower the fsync speed issues.

Also as a side note I went though my small test cluster which is 6 machines with 2 disks each (1ru servers) and replaced all of the disks which seemed to have a higher then average fsync than the other disks and this increased my clusters performance considerably and I'm not currently running any raid. I guess this may go without saying however thought I might mention it :)

Quenten Grasso

-----Original Message-----
From: Steve Thompson [mailto:sm...@cb...] 
Sent: Saturday, 31 March 2012 4:33 AM
To: Chris Picton
Cc: moo...@li...
Subject: Re: [Moosefs-users] SSDs

On Fri, 30 Mar 2012, Chris Picton wrote:

> Do those servers have bettery backed cache on the raid?  If so, are they set 
> to write-back or write-through?
>
> I have found that when running on standard SATA disks, the constant fsync is 
> what slows things down tremendously.  A battery backed write-back cache on 
> the raid card would help a lot there.

Yes, the controllers (Perc 5's and Perc 6's) have battery backup, and the
virtual disks are set to write back. Indeed, write through (such as when 
the battery is doing a learn cycle) is a great deal slower.

Steve

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