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
From:
linux-lvm-bounces@redhat.com [mailto:linux-lvm-bounces@redhat.com] On Behalf Of Larry Dickson
Sent: 19 May 2008 15:37
To: LVM general discussion and
development
Subject: Re: lvm
partition on ramdisk
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
On 5/13/08, Stuart
D. Gathman <stuart@bmsi.com>
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 <stuart@bmsi.com>
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.
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