[Moosefs-users] SSDs (was: fox and bird)

[Dr. M. J. C. <mj...@av...>]

On 03/30/2012 06:49 AM, Michał Borychowski wrote:
> Hi Michael!
>
> Do you use only SSD drives in the chunkservers? Maybe you would like to
> share some speed tests with the users on the group?
>
> And do you have SSD disk in the master server? How big is your metadata?
> Have you noticed any improvements?


Michał,

I have a small moosefs system holding ~400 GB of data, including user's 
home folders.

The master server always had SSD disks. metadata.mfs is only ~50 MB.

Performance was quite disappointing until I removed the two 1TB hard 
drives in the chunk servers and replace them with four 600 GB SSDs. The 
improvement in performance was HUGE. For a small system, they are 
definitely worth the cost.

Here is a quick test I did in a live system, comparing a 600 GB SSD in 
one chunkserver with a 1TB hard drive in the other:

http://i.imgur.com/J0wxz.png

Both chunkservers were on similar network connections (gigabit ethernet, 
same switch, jumbo frames).

I think LibreOffice was having trouble with the very long fsync times 
reported on the hard drives, particularly when accessing ~/.libreoffice. 
I don't know why the fsync times were so dreadful, but the SSDs made 
that issue go away entirely. Perhaps I could have tweaked something with 
hdparm, but it was more practical to just swap in the SSDs.

The current system is excellent, robust, stable, and even works well 
with all those applications that use sqlite files, like Firefox and 
Thunderbird (troublesome on all versions of nfs).

For a future feature enhancement, you might consider allowing the admin 
to specify that certain folders - like /fileserver/home - be assigned to 
chunks on certain disks, so that home folders could go on SSDs, while 
bulk data goes on slower disks.

- Mike