Logical Drives on a Solid State Platter

• ChrisM@Work

  SSC Guru

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  December 12, 2018 at 1:59 am

  #2016071

  Jeff Moden - Monday, December 10, 2018 8:27 PM

  rchantler - Monday, December 10, 2018 2:54 PM

  Andy DBA - Monday, December 10, 2018 2:33 PM

  rchantler - Monday, December 10, 2018 2:12 PM

  Separate logical or physical drives?

  Not sure who you're asking, but I meant "logical".  We use VMware Virtual disks.  I've never confirmed it, but I've been told performance would be exactly the same if we just put everything on one big C: drive as opposed to having separate logical drives.

  Thanks.  I think most of the comments that still like having separate drives actually meant separate logical drives as opposed to separate physical drives.  Even without VMare, where you can have a big physical RAID array and distribute the space over a set of drives if you wish.

  I WISH it could go back to separate drives so that we could take advantage of dedicated drive heads but that has become near impossible nowadays.  An array of smaller drives made for some massively fast parallel I/O, which is wicked important for both transaction log files and tempdb.  Yeah... I know, I know... SSDs have changed even that though they are quite a bit more expensive even now.

  From what I can make out (after a ton of reading), SSD's shift the queue location upstream to the controller or more usually the controller channel for the array, during a maxed-out write. You can go beyond this by using another controller channel talking to another unit of storage. At some point you will saturate and the queue goes upstream again, to the controller buffer - and you can scale up from this point by adding more controllers. At some point you will saturate the bus, and if this happens, you can (if you have deep pockets) use a second bus.

  This all seems perfectly logical to me. I'm still researching a modest home lab, and getting Dell storage people to give consistent or even honest answers has been as productive as nailing jello to a wall - and this was about their own kit.

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