This is Scientific Linux (RHEL) 6.4. That's nominally kernel 2.6.32, but that doesn't tell one much. The RHEL kernel is the RHEL kernel, with features selected from far more recent kernels included, more being added with every point release. (e.g., I have the dm-thin target available in LVM2.) I've used both CFQ and Deadline for testing. It doesn't make a measurable difference for either the multiple dd's or for the single-threaded C/ISAM rebuild. (In fact, deadline, while often better for servers, can have problems with mixed sequential/random access workloads. At least according to what I've seen over on the PostgreSQL lists. It's no surprise that deadline doesn't help my single-threaded workload. Also note that deadline has shown itself to be slightly superior to noop for SSD's in certain benchmarks.) There's no one size fits all answer. Until the particular workload is actually tested, it *is* guesswork. I/O scheuling is too complicated for it to be otherwise. The chipset supports AHCI, but unfortunately it's turned off on the PET310, and the setting is not exposed in the BIOS setup, despite the fact that Dell advertises AHCI capability. It would do AHCI if I bought one of the optional SAS controllers. Since this is an unusual RAID10 situation, and I have plenty of spare processor available, I'm going to try RAID5 over the weekend. I've never used it. But I'm guessing that parity might come at a lower bandwidth cost than mirroring. Should be a fun weekend. :-) BTW, any recommendations on chunk size? -Steve -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
