When using Nexenta it is highly recommended to attach the syspool disks via AHCI instead of SATA. Attaching them via SATA might cause I/O errors leading to complete outages. The only way to solve this is to replace the driver with AHCI.
Normally changing the driver for the syspool requires a complete reinstallation. However if you want to avoid this simple follow this guide:
- Boot with Nexenta Setup CD; Choose “Rescue System”
- when booted import the syspool with:
zpool import -f syspool
- Install boot loader on ALL disks belonging to the syspool, e.g. for the first disk:
- Export the syspool:
zpool export syspool
Done. The system now uses AHCI drivers.
This is part III of my most recent project named “Building a custom and cheap storage server yourself”. Part I can be found here and Part II here.
Part II left with a current status of a crashing machine during high I/O loads.During the previous weeks i tried to solve the stability problems. And finally: we solved them!
This third part is about our problems, what caused them and how we finally solved them….
It´s been a few months since posting the idea of building a custom made storage system in my blog. During this time we convinced people to give our idea a try, did some minor changes to the box layout and ordered the parts. Finally they arrived at 27th December 2009.
So this is part II of the project called “Building a custom and cheap storage server yourself”. For people dont know what i am talking about: part I can be found here and part III here.
Building the box
We had a budget of approx 12.000 euros for building the prototype of the storage box. We decided to build the prototype with 40 disks from the start and fit an SAN-HBA in it to try COMSTAR (this enables us to export the storage via SAN to other servers). As operating system we choose Open Solaris. Two disks are dedicated to the operating system and are attached directly to the mainboard. The remaining 38 disks are attached to either one Adaptec 52445 or one Adaptec 51645 controller.
Below are some pictures of the components and the final assembled box. Click on the image for a larger version:
Recently i came across a project where they built their own cheap storage. The whole story is documented here and here.
A colleague of me and i saw this project and wondered if this kind of storage could be used for databases as well. So we analyzed the design and noticed some problems from our point of view:
- data access only via HTTP
- they used the JFS file system which is not widely used
- generally hard disks are hot-swappable; but not used due to fear of problems
- optimized for space rather than for speed
- relatively “weak” power supply
So we tried to improve the layout with the following constraints:
- approx. 10.000 Euro (approx. 15.000 US-Dollar) in total
- Storage accessible via multiple protocols:
- if possible SAN
- Optimized for speed rather than capacity (remember: we talked about databases)
- Hot-Swapable Harddisks
This is part I of our journey towards building a storage system ourself. Part II is here and Part III here.