From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Geschke Subject: Re: bcache not working on large files? Date: Wed, 23 Oct 2013 16:47:16 +0200 Message-ID: <20131023144715.GA3373@euve30603.vserver.de> References: <20131022070830.GA20286@euve30603.vserver.de> <5266B774.6040202@rolffokkens.nl> <20131022180316.GA24473@euve30603.vserver.de> <1382476284.36900.YahooMailNeo@web181506.mail.ne1.yahoo.com> <20131022214553.GC26186@euve30603.vserver.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20131022214553.GC26186-TGNR7510c4H9eX/OD4jYIkzuTB+3w3uf@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-bcache@vger.kernel.org Hi all, > So with 8 threads doing random I/O of 4k blocks in a 1000 GB file > results in IOPS in the range of about 20,000. The same setup with > a file of 10,000 GB results in an IOPS of about 400. That is about > the same rate the HDDs have without bcache. This is something I did > not expect. It looks like bcache stopped to work at all... I have to correct it: I rebuild the SSD-RAID and used now an RAID 0 instead of RAID 6 for caching. So now I get about 10.000 IOPS with writing 4k blocks . I think this is a) ok and b) it is not a bcache problem I suspect it is a problem of the raid controller, but I have no clue which one... Probably it is a better decision to use a separate raid controller for SSD (b)cache... Best regards Dirk -- +----------------------------------------------------------------------+ | Dr. Dirk Geschke / Plankensteinweg 61 / 85435 Erding | | Telefon: 08122-559448 / Mobil: 0176-96906350 / Fax: 08122-9818106 | | dirk-tpR6ahGJfjwEZ6m2XrtfILNAH6kLmebB@public.gmane.org / dirk-WMiem5eIfR0n5izryJqWLw@public.gmane.org / kontakt-WMiem5eIfR0n5izryJqWLw@public.gmane.org | +----------------------------------------------------------------------+