On Sat, 2011-05-07 at 16:19 +0300, Dima (Dan) Yasny wrote: > On Sat, May 7, 2011 at 4:06 PM, guy keren <c...@actcom.co.il> wrote: > > > > you are stepping into "never-never" land ;) > > > > "iostat -x -k 1" is your friend - just make sure you open a very wide > > terminal in which to look at it. > > > > disks are notoriously slow, regardless of error cases. it is enough if > > an applications perform a lot of random I/O - to make them work very > > slow. > > > > i'd refer you to the slides of the "linux I/O" lecture, at: > > > > http://haifux.org/lectures/254/alice_and_bob_in_io_land/ > > > > read them through. there are also some links to pages that discuss disk > > I/O tweaking. > > > > as for the elevator - you could try using the "deadline" elevator and > > see if this gives you any remedy. > > > > if you eventually decide that it is indeed disk I/O that slows you down, > > and if you have a lot of money to spend - you could consider buying an > > enterprise-grade SSD (e.g. from fusion I/O or from OCZ - although for > > your use-case, some of the cheaper SSDs will do) and use it instead of > > the hard disks. they only cost thousands of dollars for a 600GB SSD ;) > > Would probably be cheaper to get a bunch of SATAs into a raid array - > spindle count matters after all. > > My home machine is not too new, but it definitely took wing after I > replaced one large SATA disk with 6 smaller ones in a raid5 (I'm not > risky enough for raid0) >
you are, of-course, quite right. provided that a hardware RAID controller is being used. --guy > > > > --guy > > > > On Sat, 2011-05-07 at 15:29 +0300, Omer Zak wrote: > >> I have a PC with powerful processor, lots of RAM and SATA hard disk. > >> Nevertheless I noticed that sometimes applications (evolution E-mail > >> software and Firefox[iceweasel] Web browser) have the sluggish feel of a > >> busy system (command line response time remains crisp, however, because > >> the processor is 4x2 core one [4 cores, each multithreads as 2]). > >> > >> I run the gnome-system-monitor all the time. > >> > >> I notice that even when those applications feel sluggish, only one or at > >> most two CPUs have high utilization, and there is plenty of free RAM (no > >> swap space is used at all). > >> > >> Disk I/O is not monitored by gnome-system-monitor. > >> So I suspect that the system is slowed down by disk I/O. I would like > >> to eliminate it as a possible cause for the applications' sluggish feel. > >> > >> I ran smartctl tests on the hard disk, and they gave it clean bill of > >> health. Therefore I/O error recovery should not be the reason for > >> performance degradation. > >> > >> I am asking Collective Wisdom for advice about how to do: > >> 1. Monitoring disk I/O load (counting I/O requests is not sufficient, as > >> each request takes different time to complete due for example to disk > >> head seeks or platter rotation time). > >> 2. Disk scheduler fine-tuning possibilities to optimize disk I/O > >> handling. > >> 3. If smartctl is not sufficient to ensure that no I/O error overhead is > >> incurred, how to better assess the hard disk's health? > >> > >> Thanks, > >> --- Omer > >> > > > > > > > > _______________________________________________ > > Linux-il mailing list > > Linux-il@cs.huji.ac.il > > http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il > > _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
