[BBLISA] Fileserver opinion

[Ian Stokes-Rees]

Diligent readers will recall the thread a few weeks ago on slow disk
performance with a PATA XRaid system from Apple (HFS, RAID5).  Having
evaluated the situation, we're looking to get a new file server that
combines some fast disk with some bulk storage.  We have a busy web
server that is mostly occupied with serving static content (read only
access), some dynamic content (Django portal with mod_python/httpd), and
then scientific compute users who do lots of writes (including a 100
core cluster).

We have about a $10k budget (ideally $8k).  The current plan looks
roughly like this:

AMD quad socket MB
1x12-core AMD CPU
8 GB RAM
2x160 GB 7200 RPM SATA drives for system software
11x300 GB 15000 RPM SAS2 fast storage (RAID10 + 1 hot swap, 1.5 TB volume)
5x2 TB 7200 RPM SATA drives (RAID10 + 1 hot swap, 4 TB volume)

A 3U chassis will be filled, and the 4U chassis will have some empty bays.

We can also upgrade processors and RAM as funds become available and the
need arises.

This will support a compute cluster (~100 cores), 10-20 users (typically
3-4 active), and a busy web server.

Besides the obvious question of whether this setup is sensible/cost
efficient (mixing two kinds of storage, etc.), the main unknowns we have
are:

1. Should we consider running a VM on this same server and host e.g. the
web server on a VM which accesses files through the virtualization
layer, rather than a physical network interconnect.

2. What combination of network filesystem and local file system
combination makes sense? (currently NFS + ext4 is on the cards)

3. Should we consider alternatives to GigE for interconnect.

4. How can we estimate our IOPs and throughput requirements?

5. Perspectives on SLC SSDs vs. SAS2 w/ 15k drives, since we could
probably transfer the 11x300 GB SAS2 drive budget to a collection of
SSDs and live with the reduced storage if that was expected to have a
big performance benefit.

Thanks in advance for any opinions on this.

Ian

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