On 07/02/2014 11:36 AM, George R Goffe issued this missive:
Rick, Thanks for your info. I'll check this out as well. I have used hdparm -B to get and set the APM values... All the drives including the system drive were set to 128. I have set them to 255 now so we'll see what happens. Actually, the behavior makes me think of a cache that has been emptied... My new activity has to rebuild the cache. Ideally, I'd like to make the cache bigger and have entries written back to the drive(s) BUT remain in cache... A least used algorithm could be used when looking for free space in the cache similar to the one for real memory. Do you know the developers or of a mailing list?
The filesystem cache is controlled by the kernel and the filesystem modules. Part of RAM is reserved for caches and it's shared across all the mounted filesystems IIRC. If a filesystem goes "inactive", then the stuff cached for it will eventually be expired and that RAM will be used for more active filesystems. I don't know of a way to control either the size of the cache or its retention period. It might be controllable via a sysctl, but I've never tried to bugger things like that. There are a number of resources about individual filesystems out there on the web. Google your filesystem type and you should find some. For example, http://ext4.wiki.kernel.org/index.php/Main_Page (for the ext4 filesystem).
Again, thanks for your response.
No worries, mate. Glad I could help somewhat.
------------------------------------------------------------------------ *From:* Rick Stevens <ricks@xxxxxxxxxxxxxx> *To:* George R Goffe <grgoffe@xxxxxxxxx>; Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx> *Sent:* Wednesday, July 2, 2014 10:36 AM *Subject:* Re: Fedora 19 - filesystems slow On 07/02/2014 12:49 AM, George R Goffe issued this missive: > Hi, > > I have a Fedora 19 system with several large 2-4TB drives attached via USB-SATA docking stations. > > I'm seeing a problem whereby a specific filesystem that hasn't been accessed for some time and is REALLY slow to respond to initial requests. ls -alt for example takes a substantial bit of time to respond at first but then response is acceptable after that. > > I'm trying to figure out what's happening and why and what I can do about it. It's like the buffers are empty and they need to be filled. Are there kernel tunable parameters that can be changed to avoid this problem? I can think of two things: 1) The drive was spun down because of inactivity. Try looking at the man page for "hdparm", specifically the "-B" and "-S" options. 2) Caching. If the filesystem hadn't been accessed in a while, its contents are probably no longer cached. Don't know if you can do anything about that. ---------------------------------------------------------------------- - Rick Stevens, Systems Engineer, AllDigital ricks@xxxxxxxxxxxxxx <mailto:ricks@xxxxxxxxxxxxxx> - - AIM/Skype: therps2 ICQ: 22643734 Yahoo: origrps2 - - - - Careful! Ugly strikes 9 out of 10 people! - ----------------------------------------------------------------------
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