Expected to Crash Often

May 3, 2008

Today I came across this page with some tips for NFS clusters (emphasis mine):

“The server side of NFS allows no real configuration for performance or reliability. Default asynchronous writes are not very risky unless you expect your disk servers to crash often.

Maybe the fact that the page is about redundant NFS clusters tells us that do expect the servers to crash often enough 😉


Is iSCSI NAS SAN?

May 9, 2007

If you think the title makes no sense, read this post and other posts related to the original post.

Although this will automatically put me into the mind-losing group, from the sales and non-technical marketing perspective – note the emphasis – I tend to agree with his “politically incorrect” view of iSCSI. I doubt that any of these critics have ever spent hours – I have, and it wasn’t fun – pitching their solution to the customer only to be asked “Is this NAS thing of yours that SAN thing?”

From the NetApp perspective, I guess that iSCSI indeed is Network-Attached Storage Area Network-kinda Storage. Seriously, in simple terms, it’s just another way to allocate NetApp storage to clients/hosts. Because NetApp filers are versatile (NAS, iSCSI, SAN), they don’t really need to care or argue about this with their prospects and/or customers. (Personally I think there’s a better way to provide a single solution for integrated block and file storage – more about this some other time).

Says Marc Farley:

It does not matter if the network is Fibre Channel or Ethernet (or carrier pigeons), the network is simply a way to transmit information for a storage application.

Well, this is exactly why I do not equal iSCSI with SAN. It does matter. I don’t have anything against accessing my database over FC (as long as I can afford it). And yes, in some cases I would definitively consider recommending Ethernet instead, but I would never recommend or even consider using PTP (Pigeon Transport Protocol). (Not yet, anyway. Maybe one day we’ll have storage-enabled pigeons that will be able to use spooky action at a distance to overcome limitations of PTP v1. Even with PTP v2 we’d still need a good MPIO mechanism for pigeons to prevent Single Point Of Flying, or SPOF – it’s gonna take time.)

When people hear “SAN” many of them will – maybe mistakenly, as this SAN could be Ethernet-based – visualize thin orange cables, low (lower than GbE) latencies, dedicated FC storage switches and the rest of FC-SAN h/w and s/w. I am not saying that Gigabit Ethernet and iSCSI won’t or can’t do, but it’s just not the same. What I am saying, though, is that this isn’t any more PC and/or less confusing than Dave’s opinion.

iSCSIs vendors would like you to think iSCSI is SAN and Ethernet is as good as FC, versatile storage vendors say “whatever you want, pal”, and so on and so forth. It’s (not) that simple! Devil said (not actually, but in a movie): “Consider the source, son!”

If we wanted to be technically correct or very PC from the technical point of view, we couldn’t easily communicate with decision makers and other stakeholders (assuming that everything offered satisfies requirements from the customer’s RFP, why would application owner have to care what’s happening behind that mount point?), which is why occasional technical heresy can be a skill.

P.S. By the way, whatever happened to IP-SAN? It’s been a while since I heard iSCSI vendors using this term. Did it have to go because it had a low-end (as in “Netgear launches dirt-cheap IP SAN” Ouch!) ring to it? That’s too bad, because I kind of like it and it means what it does.


New Computing Architecture

May 4, 2007

Interesting blog post at ZD IT Link:

“The chief architect of IBM’s systems thinks the industry is on the cusp on creating new computing architecture that will allow applications to run some subset of their operation on top of storage servers rather than compute servers.”

Okay, so you run some application code on pSeries and xSeries servers and some on IBM N Series (NAS filers OEM-ed from NetApp). What applications, except NDVM backup, run on NetApp’s OnTap OS? I don’t know of (m)any. Then where does N Series fit into this new architecture?

“According to Rod Atkins, IBM is building prototypes of hybrid systems that will allow portions of a database to execute directly on a storage server powered by a P series processor.”

Oops, it looks like it doesn’t. If they keep reselling NetApp, won’t IBM end up with two storage server solutions – the absolutely proprietary N Series and the relatively proprietary pSeries?

This doesn’t sound like unified storage to me: N Series for serving file, iSCSI and FC storage and pSeries storage servers for executing “portions of a database”. I hope they won’t make pSeries storage servers use storage provisioned by an N Series filer, that would be a little too complicated!