<div>The purpose was to move seeking operations onto the ramdisk (ultimately NVRAM or battery-backed), and use a file system that allocates disk sectors in sequential order for scientific (no-delete) data streaming writes. It allows near full speed writing to the main (big RAID) storage, and yet a standard file system structure appears on the recorded data at little cost. Log-structured file systems serve a similar purpose, but the structure of the data and metadata is quite complex, and an additional step of "capping" is needed if random-access reads are to be reasonably fast.</div> <div> </div> <div>Larry </div> <div>On 5/19/08, Gerrard Geldenhuis <<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:Gerrard.Geldenhuis@datacash.com" target="_blank">Gerrard.Geldenhuis@datacash.com</a>> wrote: <blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"> <div lang="EN-US" vlink="blue" link="blue"> <div> Thanks for the update. I have not followed the thread closely… did you see any significant measured peformance increase in using lvm on a ramdisk? Regards <div style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0cm; BORDER-TOP: medium none; PADDING-LEFT: 4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: blue 1.5pt solid; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none"> <div> <div style="TEXT-ALIGN: center" align="center"> <hr align="center" width="100%" size="2"> </div> From: <a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:linux-lvm-bounces@redhat.com" target="_blank">linux-lvm-bounces@redhat.com</a> [mailto:<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:linux-lvm-bounces@redhat.com" target="_blank">linux-lvm-bounces@redhat.com</a>] On Behalf Of Larry Dickson Sent: 19 May 2008 15:37 To: LVM general discussion and development Subject: Re: [linux-lvm] lvm partition on ramdisk </div> <div> Final results FYI in this investigation: A recent Ubuntu release gets past the 1TB limit. I found binaries for dosfstools_2.11-2.1ubuntu3 at <div> <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://packages.ubuntu.com/feisty/otherosfs/dosfstools" target="_blank">http://packages.ubuntu.com/feisty/otherosfs/dosfstools</a> and unpacked them with ar -x. The source is in <a onclick="return top.js.OpenExtLink(window,event,this)" href="https://launchpad.net/ubuntu/+source/dosfstools/2.11-2.1ubuntu3" target="_blank">https://launchpad.net/ubuntu/+source/dosfstools/2.11-2.1ubuntu3</a> </div> </div> <div> <div> With 4KB sectors, it defaults to 128KB clusters and reaches over 97% write speed on an 8TB volume. The ramdisk area needed is a little over 512MB, so if you use 768MB you get quite a bit of room for directories also on ramdisk, and with a little finesse you can even make the subdirectories lay themselves down on ramdisk. To be "Windows-legal" you could use 32KB clusters and a little over 2GB ramdisk (or a little over 1GB with one FAT). Linux is happy with the big clusters, and according to the design should actually be willing to go to 16TB. Larry</div> <div> </div> <div> On 5/13/08, Stuart D. Gathman <<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:stuart@bmsi.com" target="_blank">stuart@bmsi.com</a>> wrote: On Tue, 13 May 2008, Larry Dickson wrote: > on the full, unpartitioned lv. Then it mounted, with the entire FAT on > ramdisk, and wrote very fast because FAT32 (like DOS) lays down data in > order from the start of a disk and does not skip around (I'd be interested > if anyone knows any other file systems with that property). The SysV filesystem put a fixed size inode table at the beginning of a partition. More modern filesystems from ext to reiser try to distribute the meta-data to keep it closer to the data. This is, of course, counter productive when the beginning of a disk is significantly faster and seek-free as in your setup. Since ext3 inode placement is table driven (with the table in a magic inode), there is probably a simple patch to mke2fs to create only one inode table at the beginning of a drive. In fact, I wonder if there is already an option... looks like -g blocks_per_group might do the trick - assuming inodes are at the beginning of a block group, rather than the middle. If not, a patch to mke2fs is needed to do what you want. -- Stuart D. Gathman <<a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:stuart@bmsi.com" target="_blank">stuart@bmsi.com</a>> Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154 "Confutatis maledictis, flammis acribus addictis" - background song for a Microsoft sponsored "Where do you want to go from here?" commercial. _______________________________________________ linux-lvm mailing list <a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:linux-lvm@redhat.com" target="_blank">linux-lvm@redhat.com</a> <a onclick="return top.js.OpenExtLink(window,event,this)" href="https://www.redhat.com/mailman/listinfo/linux-lvm" target="_blank">https://www.redhat.com/mailman/listinfo/linux-lvm</a> read the LVM HOW-TO at <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://tldp.org/HOWTO/LVM-HOWTO/" target="_blank">http://tldp.org/HOWTO/LVM-HOWTO/</a></div> </div></div></div></div> _______________________________________________ linux-lvm mailing list <a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:linux-lvm@redhat.com" target="_blank">linux-lvm@redhat.com</a> <a onclick="return top.js.OpenExtLink(window,event,this)" href="https://www.redhat.com/mailman/listinfo/linux-lvm" target="_blank">https://www.redhat.com/mailman/listinfo/linux-lvm</a> read the LVM HOW-TO at <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://tldp.org/HOWTO/LVM-HOWTO/" target="_blank">http://tldp.org/HOWTO/LVM-HOWTO/</a> </blockquote></div>