[SATLUG] Filesystem/RAID advice

Brad Knowles brad at shub-internet.org
Sun Oct 24 23:08:09 CDT 2010

On Oct 24, 2010, at 7:30 PM, travis+ml-satlug at subspacefield.org wrote:

> In that case, yeah, you're substituting s1+h1 with s2+h2, and
> you can see more gains, since you're replacing more - not just
> hardware, but potentially inefficient software also.

In this case, I believe that most people will not necessarily fully understand (or care about) the difference between full-on hardware virtualization versus paravirtualization, what they're interested in is the final results.

> I don't really recommend those consumer NAS devices; my impression is
> that most of them tended to be underpowered CPUs with limited RAM and
> slow interfaces, limited upgradeability, limited file systems, though
> I'd be happy to be proved wrong.  It's certainly not a design
> requirement, just market forces I think ("cost per terabyte" thinking).

For the Infrant ReadyNAS system, these statements are not applicable.  I know some of the most knowledgeable people in the entire business in this segment, including guys like the technical manager of worldwide field support for Hitachi Data Systems, and he has things like multi-million dollar FibreChannel protocol analyzers that he sends out with his technicians that are going in to support some of the biggest and most important customers on the planet.  Or Curtis W. Preston, who literally wrote the book on SANs and NAS for O'Reilly -- and for which I was a technical reviewer.

And these guys think pretty highly of the ReadyNAS stuff, at least for SOHO use.  Sure, you wouldn't want to run a multi-trillion dollar business on them, you'd want real-deal HDS SANs for that, or maybe Texas Memory System RamSan devices for your highest-end Fortune 100 & Wallstreet financial firms, but for most SOHO customers, ReadyNAS is about as good as it gets, unless they're willing and able to spend the money for something like BlueArc or NetApp.

Of course, some people prefer to roll their own when it comes to file servers, but even the best home-grown systems are going to have a hard time meeting or beating the uptime, total cost of ownership, and performance capabilities that you can find baked into ReadyNAS.  You might be able to beat ReadyNAS in any one of those areas, but you are almost certainly going to have to end up giving up something in one of the other areas to do so.

> * All the discussion of NVRAM and stuff matters very little if you
> have a UPS on the server and can do clean shutdowns

UPS doesn't do you a damn bit of good when someone unplugs the server from the UPS, either without knowing what they were doing, or by accidentally tripping on a cable.  I've seen that type of failure way too often.  Hell, I've *DONE* that type of failure way too often.

UPS also doesn't do you a damn bit of good when the problem is that your admin (or your spouse) fat-fingers something and your data goes P00F!

UPS and RAID are both part of the overall solution space, but you need far more than just UPS and/or RAID.

> On file systems, I ended up using reiserfs, though I look forward to
> btrfs.

I've always had serious reservations about ReiserFS.  The more I looked into it, the more it looked like the Wizard hiding behind the curtain -- and the Wizard had no clothes.  And since Hans Reiser was convicted of murdering his wife, I got the impression that the whole thing kind of just shriveled up and died.

XFS is something I came to have a great deal of trust in, at least the fully-baked version on SGI Irix.  I never got the feeling that XFS on Linux had ever gotten anywhere remotely close to that same level of robustness and reliability.

I still have some questions in my mind about ZFS, but of all the "modern" filesystem replacements that have come along, it seems to be the one that has had the most real work put into it to make it both truly robust and performant -- at least on Solaris.  I'm not so sure about ZFS on OpenSolaris or FreeBSD, but I would at least be willing to give it a shot.

Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>

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