On 18 December 2014 at 20:26, Mark Post <[email protected]> wrote: > > >>> On 12/18/2014 at 09:32 AM, "Levy, Alan" <[email protected]> wrote: > > Does it make sense in just setting up one mod 29 (32000+ cylinders, app > 21G) > > and let the btrfs use the whole thing instead of breaking it up into > smaller > > pieces (var, opt, home, etc) ? > > Without anything to back this up, my concern is that having everything on > one virtual device number might cause I/O performance problems. Hopefully > someone who does performance analysis for a living is looking at various > layouts and will talk about their results. >
I think we agree that carving up a single disk into multiple partitions will not increase your I/O bandwidth. It may be useful for managing the system as Offer suggested. Some also believe that we do not want the system to continue when it is unable to write log files etc. YMMV. You rarely see the Linux operating system and utilities itself do I/O as heavy that you need to worry. Spreading mount points over multiple minidisks for performance reasons seems overkill and tedious. And no, half a dozen partitions on the PC hard disk don't achieve that either. But there may be other good reasons to put /home apart from the rest for example. If you have an application that does a lot of disk I/O, it makes sense to separate that so you can design and tune the disk I/O subsystem for that. That design may involve multiple logical disks to increase throughput, depending on the application and the workload. For example you don't want your database and redo log files on the same disk because I/O patterns are different. You might be able to avoid that with PAV (but only for some workload patterns) but I'm not sure it's wiser. Quite often application I/O requirements are moderate and don't require a single server to monopolize the entire I/O subsystem. There's too many aspects to cover on a Friday afternoon. Rob PS As long as some middleware considers /tmp the ideal place to archive (multiple) installation log files, I don't want that in VDISK. In many cases the 'true' /tmp usage is so brief that it does not even touch the metal but I don't need another copy in memory if it does... ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
