|Summary:||Slow raid and scsi function|
|Product:||[Retired] Red Hat Linux||Reporter:||Need Real Name <cl>|
|Component:||kernel||Assignee:||Arjan van de Ven <arjanv>|
|Status:||CLOSED WORKSFORME||QA Contact:||David Lawrence <dkl>|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2003-06-06 14:28:03 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
Description Need Real Name 2001-07-10 16:42:53 UTC
From Bugzilla Helper: User-Agent: Mozilla/4.72 [en] (X11; U; SunOS 5.6 sun4u) Description of problem: Raid systems seem to have problems. How reproducible: Always Steps to Reproduce: 0. hdparm -t /dev/sda1 1.18 MBps 1. set up stock raidtab with 2 scsi drives From the Software Raid HOW-TO. 2. mkraid /dev/md0 3. mkfs /dev/md0 4. hdparm -t /dev/md0 600 KBps Actual Results: Raid was slower that the single drive. When I take the raid 0 to 6 drives data rate drops to around 100KBps. When attempting to move data to the 6 disk raid0 drive the kernel will panic. The effect worsens with the use of raid 4 and raid 5. Expected Results: I would expect a faster response time from a raid0 config with 2 drives and and much faster response time from a raid0 with 6 drives. Additional info: System: 1 P100 64 Megs Ram 1.6 gig IDE HD AHA1542 Scsi Card 7 IBM 1050m scsi drives System : 2 P166 64 megs Ram 1.05 gig IDE HD AHA1542 SCSI Card 7 IBM 1050m scsi drives I have been doing raid testing on RH7.1 I have yet to see it work worth a flip. Cards tested 2 AHA1542, AHA2920,2 FDomain 18xxx cards I have also tested on the 7 IBM drives, 4 Quantum, 5 Seagate, 3 Conner drives (all scsi).
Comment 1 Elliot Lee 2001-08-26 20:40:38 UTC
Get faster hardware? :) The problem is with your method of benchmarking. I too get a slightly slower hdparm -t time on a raid0 array (six devices) than I do from an individual disk in the array. I attribute this to the overhead that the RAID code has compared to direct disk access. However, if I do something slightly more realistic (timing a 'dd' of a 256M file from the same raid0 array compared to a single hard disk), the raid0 array wins The kernel panic is something that is bad and a more specific problem than "it's too slow" - I am reassigning this bug to the kernel in hopes that you will provide the maintainers with details of that problem.
Comment 2 Arjan van de Ven 2001-08-26 20:47:51 UTC
A few questions for the performance first: * what stride-size did you set the raid0 to ? * could you use the tiobench program (http://sourceforge.net/projects/tiobench ) instead of hdparm as that will test FILE access and not raw io access. (the kernel will do things like readahead on files, not on devices) * what kernel version did you try ? 2.4.2-2 or 2.4.3-12 ? You mention a "panic". Any chance of gettin any info of that so we can try to find the bug ?
Comment 3 Alan Cox 2003-06-06 14:28:03 UTC
Closing idle bug