thinking sysadmin

Paul Manning, from VMware, in response to a question I asked in the VI:OPS forums:

The current best practice for NFS is to not seperate the VM swap space from the VMhome directory on a NFS datastore. The reason for the originial recommendation was just good old fashioned conservitiveness.

More at the forum post, including more on the reasoning for the old recommendation of separating swap when using NFS – thanks, Paul, you made my day.

• Your Usable Capacity May Vary – Chuck conducts a thought deployment comparing EMC, HP and NetApp usable space for a 120 disk Exchange deployment. And while he glosses over a couple perhaps non-minor issues (RAID-5 vs RAID-DP and whether EMC’s snapshots are adequately performant), he does hit one of NetApp’s weak spots dead on: Usable capacity, particularly on LUNs if you follow the 100% space reservation recommendation. (Being a NetApp admin these days, I can’t really comment on what he writes about HP – it’s been a long time since I’ve touched that StorageWorks stuff – and I can only repeat what I’ve heard others say about EMC.) More Chuck on this here.
• How to License Windows VMs in a Non Microsoft Virtual Environment: Why Windows Server 2008 Datacenter Edition may be the best choice. (Seen at blog.scottlowe.org.)
• Welcome – My friend, NetApp’s Vaughan Stewart: Chad Sakac highlights some flaws in NetApp’s TR-3697 (“Performance Report: Multiprotocol Performance Test of VMware® ESX 3.5 on NetApp Storage Systems”):
  

  What’s the scoop with:

  * 4K/8K IO size only
  * 2Gbps FC
  * You guys have “throughput/IOPs” shown only in relative, not in absolute.
  * 84 144GB drives with 16 VMs driving the IOMeter workloads with * 10GB of data each on them = 1.3% utilization (rounding up!).

• Performance Report: Multiprotocol Performance Test of VMware® ESX 3.5 on NetApp Storage Systems: A complementary whitepaper to VMware’s own work comparing Fibre Channel, iSCSI and NFS as storage protocols for VMware ESX. (Seen at blog.scottlowe.org.)

• Amazon S3 Availability Event: July 20, 2008 – Amazon’s post-mortem on the 7/20 S3 outage. Excerpt: “We’ve now determined that message corruption was the cause of the server-to-server communication problems. More specifically, we found that there were a handful of messages on Sunday morning that had a single bit corrupted such that the message was still intelligible, but the system state information was incorrect.” (Seen first at Ars Technica.)
• VMware has released Update 2 for VMware Infrastructure 3 version 3.5 (I think that’s the Full Official Name That Only A Committee Could Love…). Scott Lowe has a good summary; release notes are here. Most notable among the updates is the ability to use VSS to quiesce Windows VMs prior to snapshotting.

• VM HA – service console networking, isolation behavior – and other “under the covers stuff” – An overview of how VMware ESX’s High Availability works under the hood – making it much more apparent to me how important file locking is to HA’s functioning. (I’d love to see an overview of how file locking does – or doesn’t – differ on VMFS versus NFS datastores.)
• Why Upgrade? – DanT on what’s new in Sun Grid Engine 6.0 through 6.2.
• Part II: Since NFSv4 is Stateful It Must Be Less Robust, Right? – “Just because CIFS is old and busted, that doesn’t mean NFSv4 is.” Just kidding, that’s not an actual quote. But I think it’s a reasonable summary of the piece.
• HP – Performance-Optimized Data Center – Yet another vendor produces a data center-in-a-box product – which isn’t to say that there isn’t good technology inside of HP’s product. I wonder if container data centers will come down-market to the point where they become a reasonable alternative for new office building construction instead of building a conventional server room. (Seen at Data Center Knowledge.)
• Understanding NIC Utilization in VMware ESX – Scott Lowe comes through again with another practical piece on networking and VMware ESX.

• Red Hat adopts KVM: what happens to Xen now? – I work in a VMware ESX shop right now (other than all those Solaris Zones and FreeBSD Jails and OpenVZ VEs, that is) – no Xen or KVM. However, given the serious pain in the butt that timekeeping is in Linux guests on ESX, I’ve been sorely tempted to look at running Xen for some Linux virtuals under CentOS 5, in the hopes that this isn’t a problem there. Guess I’ll hold off on that now. (Yeah, I’ve read all the docs, and Linux time sync generally sorta kinda usually works until it doesn’t – it just shouldn’t be that much of a flail.)
• 10 Gigabit Ethernet and VMware – A Match Made in Heaven – Lengthy and interesting article on 10GbE, VMware, consolidation and datacenter Ethernet – dismissive of Infiniband’s chances of becoming the One True Network Fabric.
• Blocks and Files: Between a server or storage array place – More commentary on Chuck’s commentary on HP’s flash announcement. Quote: “Another aspect of this is that a flash SSD cache for a servers needs to plug in to the server’s bus and the supplier doesn’t have to worry about getting a Fibre Channel interface onto flash SSDs which is needed to plug them into existing Fibre Channel slots in a storage array. STEC has an effective monopoly on this (with EMC having its own mini-monopoly because of its exclusivity deal with STEC which ends in a few months) until Emulex’ SSD-tweaked SATA-to-FC bridge chip becomes available at the end of the year. ” Which is probably why NetApp recently announced this instead of flash drives.

VMware has just released a paper entitled Comparison of Storage Protocol Performance (seen at Scale the Mind and blog.scottlowe.org); maybe this will help deflate some of the too-often repeated speculation that NFS is too slow for VMware ESX.
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