For some reason, I've been working on lots of Exadata V2 systems in the past few months. One of the issues that I've been coming across for these clients is a failure in the battery that is used by the RAID controller. It was originally expected for these batteries to last 2 years. Unfortunately, there is a defect in the batteries where they reach their end of life after approximately 18 months. The local Sun reps should have access to a schedule that says when the "regular maintenance" should occur. For one client, it wasn't caught until the batteries had run down completely and the disks were in WriteThrough mode. This can be seen by running MegaCLI64. Here is the output to check the WriteBack/WriteThrough status for 2 different compute nodes (V2 is first, X2-2 is second):
[enkdb01:root] /root > dmidecode -s system-product-name SUN FIRE X4170 SERVER [enkdb01:root] /root > /opt/MegaRAID/MegaCli/MegaCli64 -LDInfo -LALL -aALL | grep "Cache Policy" Default Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteThrough, ReadAheadNone, Direct, No Write Cache if Bad BBU Disk Cache Policy : Disabled
[root@enkdb03 ~]# dmidecode -s system-product-name SUN FIRE X4170 M2 SERVER [root@enkdb03 ~]# /opt/MegaRAID/MegaCli/MegaCli64 -LDInfo -LALL -aALL | grep "Cache Policy" Default Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU Disk Cache Policy : Disabled
If you have a V2 and you haven't replaced the batteries yet, it's worth running these commands to see what state your RAID controllers are in. To find out what this means for you, read on after the break.
As business has picked up since OpenWorld (didn't think that was possible, but that's another story for another day), we have been seeing more customers adopt or seriously look at Exadata as an option for new hardware implementations. While many will complain that there isn't enough room for customization in the rigid process of configuring an Exadata system, there are still many possibilities to make your Exadata your own, whether it's during the initial configuration phase or shortly thereafter. Of course, some of these modifications can be difficult to implement after the system is up and running with users logging in. I'm planning on starting a series of posts regarding a couple of the hot-button topics with regard to Exadata configuration - ASM diskgroup layout (the topic for today), role separated vs standard authentication, and so on. As these topics have no right answers, I'm more than open to a dialogue where you may disagree. On to the good stuff!
A Quick Primer - The Exadata Storage Architecture
Ok...so we're looking at Exadata specifically in this post. In the examples listed below, we'll discuss a quarter rack, since it's the easiest to diagram. To expand to half or full racks, just adjust the number of cells (7, 14) and disks (84, 168) accordingly. To see the relationship between the compute nodes (database servers), Infiniband switches, and storage servers refer to figure 1:
Figure 1 - Exadata Infiniband/Storage Connectivity
We've had a few weeks to play around with the ODA in our office, and I've been able to crack it open and get to into the software and hardware that powers it.
For starters, the system runs a new model of Sun Fire - the X4370 M2. The 4U chassis is basically 2 separate 2U blades (Oracle is calling them system controllers - SCs) that have direct attached storage on the front. Here's a listing of the hardware in each SC:
|Sun X4370M2 System Controller Components
(2 SCs per X4370M2)
|CPU||2x 6-core Intel Xeon X5675 3.06GHz|
|Memory||96GB 1333MHz DDR3|
|Network||2x 10GbE (SFP+) PCIe card
4x 1GbE PCIe card
2x 1GbE onboard
|Internal Storage||2x 500GB SATA for operating system
1x 4GB USB internal
|RAID Controller||2x SAS-2 LSI HBA|
|Shared Storage||20x 600GB 3.5" SAS 15,000 RPM hard drives
4x 73GB 3.5" SSDs
|External Storage||2x external MiniSAS ports|
|Operating System||Oracle Enterprise Linux 5.5 x86-64|
Pictures of a real live ODA after the break.