Messages in this thread | | | Date | Tue, 20 Mar 2012 09:50:08 +0000 (GMT) | From | Holger Kiehl <> | Subject | Re: [patch v2 0/6] Add TRIM support for raid linear/0/1/10 |
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Hello,
On Tue, 20 Mar 2012, Shaohua Li wrote:
> 2012/3/20 Holger Kiehl <Holger.Kiehl@dwd.de>: >> Hello, >> >> >> On Fri, 16 Mar 2012, Shaohua Li wrote: >> >>> The patches add TRIM support for raid linear/0/1/10. I'll add TRIM support >>> for >>> raid 4/5/6 later. The implementation is pretty straightforward and >>> self-explained. >>> >>> v1->v2: >>> 1. fixed a checking issue >>> 2. dropped discard request plug and replace it with no discard merege, >>> because >>> current SCSI layer can't handle discard request merge. >>> >> Have tested TRIM patches on three different systems with the following >> hardware/ setup: >> >> 1) root mounted on a raid1 over two SAS SSD's (200GB) and /home partition >> on a raid0 over a fusionio ioDrive Duo. Is very new and seen very >> little usage. >> >> 2) root and /home mounted on a raid0 over two Intel X25 Postville >> (160GB) connected to a Intel P55 Express chipset. Has seen very >> heavy usage for approx. 2 years. >> >> 3) root and /home mounted on a raid0 over three OCZ-VERTEX2 (120GB) >> connected via ICH7 south bridge. Has seen mild usage for approx. >> 1.5 years. >> >> Made the following observations when running my own benchmark which >> copies around a lot of small files and deletes them. The benchmark on >> all systems was always run only on the /home partition ie. on a raid0. >> >> For system 1) there is hardly any measurable differnce whether discard >> is enabled or not (~29000 files per second). >> >> On system 2) the performance drops from 6500->3700 files per second, >> but under normal usage one does not notice any difference. > do you have the blktrace data when the benchmark is running, especially > when doing file deletion. I'd like to check the latency of discard in this case. > It is uploaded on ftp://ftp.dwd.de/pub/afd/test/trim
>> System 3) has problems during boot, it is so slow that some operations >> receive a timeout during boot: >> >> udevd[474]: timeout '/sbin/blkid -o udev -p /dev/md0' >> udevd[474]: timeout: killing '/sbin/blkid -o udev -p /dev/md0' [866] >> systemd[1]: dev-md3.swap activation timed out. Stopping. > In this one, discard request is slow. And per SATA standard, discard request > can't be parallel, so only one request one time, which further slows it down. > Ok, so having three disc in a raid 0 is even worth.
>> Even removing discard does not help and the above errors happen during >> boot and booting takes a long time. > this doesn't make sense. If you don't mount with discard option, no > discard request > is issued. > I read some where that swap uses discard by default and if I remember correctly it initializes the whole swap area at boot. So doing that over three disks might explain why I get those timeout error messages and after boot these commands work without delay.
Regards, Holger | |