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  1. #1
    Join Date
    Oct 2006
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    Unanswered: SAS Archetecture performance question

    Sorry; not sure what forum to ask so here goes - it's at least a SQL Server 2005 Standard installation:

    Question: Is a single SAS port connected to 10 drives nearly as fast as 10 individual SAS ports connected directly to the same 10 drives in a SQL Database environment. 15K RPM 6GBit/s SAS drives on an HP P410 RAID controller with 4 RAID volumes (RAID1 x 3 plus RAID 1+0 x 1 for mdf files).

    I'm torn between the HP Proliant 100 DL series or 300 DL series and this is the most relevant difference between them, IO wise.

    The DL100 series connects all bays to a single SAS port, even in the 12 LFF bay configuration. So it's similar to Parallel SCSI in that respect.

    The DL300 series has a separate SAS port for each physical drive. So; each drive gets it's own 6Gbit/s channel.

    It's a no-brainer that the shared single-port design will get collisions but at 6GBit/s, does it really matter for only 10 drives?

    The nature of Databases and RAID striping is that most drives will simultaneously burst transmission so I started wondering if there could be a much more serious impact than one might think.

    The HP Sales Rep said not to worry, there's no real difference with just 10 drives. Salesrep promise = red flag and fact check time.

    PS: The exact models are DL180G6 (2U and 40lbs) vs. DL370G6 (4U and 100lbs). The DL380G6 (2U) has complications when exceeding 8 drives - the 2nd cage eliminates the CDROM needed for easy installs. The DL180G6 allows rear-mounted CDROM.

    Thanks!
    Last edited by vich; 12-18-09 at 14:27. Reason: added PS

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