August 9, 2007 at 10:00 am
Hi,
We currently have a SAN with x8 300gb physical disks. There are two LUNs, one for each of our two sql server boxes. Each LUN has one logical drive which stores all database data and log files. Each drive is set to RAID 10.
Please could you help me answer the following questions:
1) Are different parts of the same physical disk shared across multiple LUNs? i.e Can heavy ReadWrite operations on one sql server impede on the performance of the other?
2) Should we create a second LUN for each server to store the log files on?
3) Is there anything else we should be considering?
Thanks
Jon
August 10, 2007 at 7:28 am
I'm not a SAN expert, and I really recommend talking to an engineer from your vendor because different SANs work differently, but...
1. Possibly. You don't want this, or I don't. I want to know which physicals are on which LUNs and only want one LUN per physical. Otherwise I lose a layer of tuning.
2. I would. I prefer to keep the logs separate so the data isn't on the same LUNs if it blows up. At least we could recover the log or the data. Also, logs write sequentially, so heads don't move much. Data is random. Fundamentally different access patterns.
March 15, 2009 at 11:12 am
This configuration is a bit light on resources for a single server, let alone two. A total of eight disks does not give you enough IOPS and as Steve noted, sounds like physical spindles will be shared between write types (and servers).
IF this is a very low volume environment and you plan your upgrades carefully you my be able to meet your needs.
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