Iscsi on Evan Hoffman

Compellent "future proof?" Not so much.

Wed, 21 Dec 2011 23:39:33 +0000

So, I’ve written about Compellent a few times from a price perspective, mostly on the disk side. I was recently contacted by our vendor with quotes for two new Compellent controllers. “What’s this all about?” I asked. “Why don’t we have a call with Compellent to discuss?” he replied. I rolled my eyes a little but figured it was worth hearing them out, since our Compellent SAN is at the heart of our infrastructure.

Do I still need swap space?

Thu, 11 Nov 2010 14:36:49 +0000

About three years ago I replaced our primary database. For years we’d been plagued by awful performance in the database and we were never able to diagnose the problem. The original server was a real beast at the time: 8 Opterons (single core), 32 gigs ram, and a fibre channel RAID connected via a QLogic HBA. This was back in 2005, so those specs don’t probably sound that impressive today, but this was a crazy configuration (with a crazy price tag to match). On paper it looked like this server should be basically invincible but the performance was awful, slowing down every process within the company. We contacted a few different companies (including CommandPrompt, which employs several of the core Pg devs) to see if they could assist us in diagnosing the problems but tuning only helped to a point. There was just something wrong with the box, maybe having to do with the FC HBA itself (which nobody knew much about).

The VMware datastore LUN 2TB (well, 1.99999 TB) size limit

Fri, 24 Sep 2010 16:00:15 +0000

I started migrating our physical machines to VMs using VMware a few years ago and the first problem I ran into is still the most annoying one: the size limit for LUNs is, per VMware’s docs, (2TB - 512B). That’s 512 bytes shy of 2TB, so basically 1.99999 TB, or 2047.999 GB. So when I create a new LUN for a datastore in the SAN the max size is 2047 GB. Now, as the VMware KB article states, this is a limitation of SCSI, not VMware per se, but that doesn’t make it any less annoying. When I first setup ESX, I created a 5 TB LUN for the datastore. It showed up in vCenter as 1 TB. After some Googling I learned of the 2 TB limit – the usable space is basically usable space = (size of lun) % 2TB, where % is the modulo operator – and found something suggesting using extents to expand the datastore across luns. I did that, but I later learned that there seems to be a consensus that extents should be avoided.

The bright side of Compellent

Wed, 22 Sep 2010 16:07:46 +0000

Since I was bemoaning Compellent’s pricing recently I figured it would be unfair of me not to highlight the upside. Their tagline is (or was when we purchased it) “The only SAN so sophisticated it’s simple.” While I can’t say whether they’re the ONLY one, the idea is definitely true. This is the first SAN I’ve ever used, and aside from the learning curve for iSCSI itself (targets, spinup delay, etc.) it’s totally simple and intuitive. Create LUNs, map them to servers. Don’t worry about things like RAID levels or hot disks. We’re into our second year with Compellent and it’s definitely lived up to its promise of simplicity.

Oh, Compellent... again with the disk prices.

Wed, 25 Aug 2010 00:57:04 +0000

Time to expand the SAN again.

I planned and budgeted for this this year but it still pisses me off. Look, I realize these guys have to make money, but the bottom line is they’re charging over $1.40/GB for SATA storage. There are 7200 RPM 2TB SATA drives on Amazon and Newegg ranging in price from $130 to $220. That’s as low as $0.065/GB. There was even a 2TB WD “Green” drive (sub-7200 RPM, I think 5900 RPM) on Slickdeals today for $99. That’s 5 cents per gig.