" This is one of the skimpiest specification sheets that I have ever seen for an enterprise product."
At least it shows the latency. This is some kind of technology cult, I've wondered into. I won't respond further. -----Original Message----- From: Bob Friesenhahn [mailto:bfrie...@simple.dallas.tx.us] Sent: 2009-10-20 21:54 To: Richard Elling Cc: Dupuy, Robert; zfs-discuss@opensolaris.org Subject: Re: [zfs-discuss] Sun Flash Accelerator F20 On Tue, 20 Oct 2009, Richard Elling wrote: >> >> Intel: X-25E read latency 75 microseconds > > ... but they don't say where it was measured or how big it was... Probably measured using a logic analyzer and measuring the time from the last bit of the request going in, to the first bit of the response coming out. It is not clear if this latency is a minimum, maximum, median, or average. It is not clear if this latency is while the device is under some level of load, or if it is in a quiescent state. This is one of the skimpiest specification sheets that I have ever seen for an enterprise product. >> Sun: F5100 read latency 410 microseconds > > ... for 1M transfers... I have no idea what the units are, though... bytes? Sun's testing is likely done while attached to a system and done with some standard loading factor rather than while in a quiescent state. > ...at the same time they quote 119,790 IOPS @ 4KB. By my calculator, > that is 8.3 microseconds per IOP, so clearly the latency itself doesn't > have a direct impact on IOPs. I would be interested to know how many IOPS an OS like Solaris is able to push through a single device interface. The normal driver stack is likely limited as to how many IOPS it can sustain for a given LUN since the driver stack is optimized for high latency devices like disk drives. If you are creating a driver stack, the design decisions you make when requests will be satisfied in about 12ms would be much different than if requests are satisfied in 50us. Limitations of existing software stacks are likely reasons why Sun is designing hardware with more device interfaces and more independent devices. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
