On Oct 18, 2010, at 6:52 AM, Edward Ned Harvey wrote: >> From: Richard Elling [mailto:richard.ell...@gmail.com] >> >>> http://www.mail-archive.com/zfs-discuss@opensolaris.org/msg41998.html >> >> Slabs don't matter. So the rest of this argument is moot. > > Tell it to Erik. He might want to know. Or maybe he knows better than you.
You were the one who posted this. If you intend to follow citations, then there are quite a number of useful discussions on resilvering in the 2007-2008 archives. >> 2. Each slab is spread across many disks, so the average seek time to >> fetch >> the slab approaches the maximum seek time of a single disk. That means >> an >> average 2x longer than average seek time. >> >> nope. > > Anything intelligent to add? Or just "nope" The assertion that an average 2x longer than average seek time is wrong. This is all done in parallel, not serially, so there is no 2x penalty. >> Seeks are usually quite small compared to the rotational delay, due to >> the way data is written. > > I'm using the term "seek time" to reference from time the drive receives an > instruction, to the time it actually is able to read/write the requested > data. In drive spec sheets, this is often referred to as "seek time" so I > don't think I'm misusing the term, and it includes the rotational delay. It is important because you have concentrated your concern based on seek time. Even if the seek time were zero, you can't get past the rot delay on HDDs. For reads, which we are concerned about here, the likelihood of data existing in the track cache is high and so the penalty of a blown rev is low. >> 4. Guess what happens if you have 2 or 3 failed disks in your raidz3, >> and >> they're trying to resilver at the same time. Does the system ignore >> subsequently failed disks and concentrate on restoring a single disk >> quickly? >> >> No, of course. >> >> >> Or does the system try to resilver them all simultaneously and >> therefore double or triple the time before any one disk is fully >> resilvered? >> >> Yes, of course. > > Are those supposed to be real answers? Or are you mocking me? It sounds > like mocking. > > If you don't mind, please try to stick with productive conversation. I'm > just skipping the rest of your reply from here down, because I'm considering > it hostile and unnecessary to read or reply further. If you want to recommend configurations and compare or contrast their merits, then you should be able to defend your decisions. In engineering, this would be known as a critical design review, where the operational definition of "critical" is expressing of involving an analysis of the merits and faults of a work product incorporating a detailed and scholarly analysis and commentary. While people who are not experienced with critical design reviews may view them as hostile, the desire to achieve a better product or result is the ultimate goal. Check your ego at the door. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
