On Fri, Sep 11, 2009 at 12:48 PM, Chris Du <dilid...@gmail.com> wrote:
> >>Can you use SATA drives with expanders at all? (I have to stick to > enterprise/nearline SATA (100 EUR/TByte vs. 60 EUR/TByte consumer SATA) for > cost reasons). > > Yes you can in E1 model. E1 is single path model which supports both SAS > and SATA. You need to know what you are buying. The Supermicro case you buy > has backplane with SAS expander. > > In E2 model which supports multipathing, dual-port is required because each > path needs access to the disk at the same time, thus SAS is required, SATA > is single-port. If you want more bandwidth between your HBA and disks and > better redundancy, you need multipathing so E2. > > I still suggest you go with nearline SAS. SAS is dual-port design, it has > much better IOPS, command queue and error recovery. Data transfer speed is > same between NS2 SAS and SATA. I know a lot of people have big problem with > 7200.11 but this is not the same disk. It does cost even more than > enterprise SATA. > > We have SATA disk shelves in NetApp, I say SATA doesn't belong to > Enterprise. Granted, SATA is only used in dev environment, production uses > 15K FC disks which we never have performance issue. > > The reason I use external disk shelf is I ran out of disk trays in head > unit. Adding SAS shelf is the quick, easy and cheap way to expand storage. I > won't touch cluster file system as it gets too complicated and way toooooo > expensive. > Better IOPS? Do you have some numbers to back that claim up? I've never heard of anyone getting "much better" IOPS out of a drive by simply changing the interface from SATA to SAS. Or SATA to FATA for that matter. A 7200RPM drive is limited by the 7200RPM's, not the interface it's attached to. --Tim
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