From mboxrd@z Thu Jan 1 00:00:00 1970 From: PFC Subject: Re: reiserfs performance on ssd Date: Fri, 28 Apr 2006 09:07:21 +0200 Message-ID: References: <20060427151655.8b771812.pegasus@nerv.eu.org> <20060427134702.GA8202@favonius> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: List-Id: Content-Type: text/plain; format="flowed"; delsp="yes"; charset="us-ascii" To: reiserfs-list@namesys.com While I like the idea, the iram implementation is horrible for various reasons : - no ECC - It uses SATA hence only a very little part of the RAM speed is used, and large latencies are introduced. - I wouldn't trust it for critical data. Then, it would be faster to just add the RAM on the motherboard and create a ramdisk... Also : THE PCI BUS MUST DIE ! It's no wonder reiserfs is slower on this thing ; reiserfs is optimized for hard disks which have high seek latencies. For RAM storage, things like hash tables are a lot better than trees, because you don't care about sequential scanning and locality of reference... (as long as the items are a bit larger than a cache line, which is obviously the case here). A filesystem that pauses and thinks for 0.5 ms of CPU time to avoid a 5 ms HDD seek time is a good thing, but for SSD storage you want a FS that doesn't think at all. Using ReiserFS on this is like hitting a nail with a screwdriver. Try tmpfs, I'm curious about the results. Crazy idea : - Ask the motherboard manufacturer to stick a battery on the mobo so that the contents of RAM survive reboot - Tweak the BIOS so that RAM isn't cleared at boot - Teach the Kernel to be cautious while booting and not overwrite the previous RAMDISK - You have persistent ramdisk. Stick your reiserfs journal on it, enjoy.