On Sat, May 7, 2011 at 4:41 PM, guy keren <c...@actcom.co.il> wrote: > 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. >
I've seen performance increases even using fakeraid (the feared intel matrix 8.x in my machine) and mdadm. Especially in a machine that has a UPS (to step in instead of a BBU) and, like mentioned above - lots of crunchpower > --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
