Solid State Store, Cheap and Fast Use DDR3 Memory, Linux and mdadm
Posted in Uncategorized on September 28th, 2010 by adminSo you want to have extremely fast storage. You also don’t have a boat load of money sitting around to do it with. Well I have a solution. I’ve been experimenting with mdadm and /dev/ram on my system the size of memory disk are 64MB so for testing I’ve created a raid array to see just how fast my memory would act as a ram drive.
#sudo mdadm –create /dev/md3 –level=0 –raid-devices=8 /dev/ram0 /dev/ram1 /dev/ram2 /dev/ram3 /dev/ram4 /dev/ram5 /dev/ram6 /dev/ram7
mdadm: metadata format 00.90 unknown, ignored.
mdadm: metadata format 00.90 unknown, ignored.
mdadm: array /dev/md3 started.
#sudo mke2fs /dev/md3
#sudo mount /dev/md3 /mnt/
#df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md3 496M 2.3M 468M 1% /mnt
So I get just about a 500 meg ram disk. So then running the following command yield rediculous speeds. Even when were talking about 500megs. Their are easily affordable system with 16gigs of ram, creating a 12gig wouldn’t be that hard to create. Might need to increase the size of ram disk but still. Once you see these numbers. Well here they are.
I did the first test with 4 ram disk in a raid 0. Here are the results.
#/opt/1$ sudo hdparm -t /dev/md4
/dev/md4:
Timing buffered disk reads: 254 MB in 0.34 seconds = 743.04 MB/sec
#/opt/1$ sudo hdparm -t /dev/md4
/dev/md4:
Timing buffered disk reads: 254 MB in 0.35 seconds = 734.65 MB/sec
Now like above I redid the test with the 8 ram disk in a raid 0.
/dev/md3:
Timing buffered disk reads: 510 MB in 0.54 seconds = 936.91 MB/sec
/dev/md3:
Timing buffered disk reads: 510 MB in 0.54 seconds = 937.48 MB/sec
Running the same test on a 500gb plater Seagate 7200.12 I get
#sudo hdparm -t /dev/sdb1
/dev/sdb1:
Timing buffered disk reads: 376 MB in 3.01 seconds = 124.93 MB/sec
Thats a 10x improvement when compared to a regular harddrive. Their are probably other factors to consider.
But one thing this tells me is that I could create a ram disk raid it and then sync data to it that I need to be able to read at a ridiculously rate. With more memory their are more possibilities. Now if only the hardware solution to this wasn’t so ridiculouslyy over priced.
With out the raid I got even better performance you can adjust the size of ram disk, but I haven’t experimented with it my self.
~$ sudo hdparm -t /dev/ram0
/dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = 1469.95 MB/sec
:~$ sudo hdparm -t /dev/ram0
/dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = 1711.82 MB/sec
:~$ /dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = /dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = 1637.50 MB/sec
ron@router:~$ sudo hdparm -t /dev/ram0
/dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = 1568.40 MB/sec
MB/sec
$ sudo hdparm -t /dev/ram0
/dev/ram0:
Timing buffered disk reads: 64 MB in 0.04 seconds = 1568.40 MB/sec