| Comments | Tag: syslife

NFS attribute caching performance impact on web applications

A couple of days ago, I had some issues with NFS consistency, not every servers were up to date. Some servers had the good version of the file some hadn’t. However performing a ls -l seemed to fixed tempory the problem after each update (where a simple ls didn’t). Indeed issuing ls with the -l option triggers stat() where ls doesn’t, just because file attributes are called from the stats() function. I needed to investigate…

Read On...

| Comments | Tag: syslife

Introducing FlashCache

FlashCache is a generic write back block level storage caching solution developed by Facebook. It’s actively used in production within Facebook and released as GPL v2 license.

Read On...

| Comments | Tag: syslife

DRBD split-brain in Pacemaker

Working with DRBD it’s not always easy, espacially when you add extra layer like pacemaker to bring high-availability to your platform. I’ve recently been through a weird issue with my high fault tolerance pacemaker cluster which is composed of 3 resources:

  • IPaddr2
  • LSB nfs-kernel
  • DRBD

Read On...

| Comments | Tag: syslife

MAASively buggy?

Couple of days ago Canonical annonced his new tool called MAAS, Metal as a Service. It makes it easy to set up the hardware on which to deploy any service that needs to scale up and down dynamically. With a simple web interface, you can add, commission, update and recycle your servers at will. As your needs change, you can respond rapidly, by adding new nodes and dynamically re-deploying them between services. When the time comes, nodes can be retired for use outside the MAAS. First test, impressions and some feedback.

Read On...

| Comments | Tag: syslife

Working with time

I’m late, I’m late, For a very important date. No time to say “Hello, Goodbye”. I’m late, I’m late, I’m late, I’m late! When you setup a new environment, it’s critical to setup the right and the same time on each servers.

Read On...