tier_setup -f /dev/sdo:/dev/sdp:/dev/sdq -c

NOTE : -c means create (format)

To assemble the tier device later:
tier_setup -f /dev/sdo:/dev/sdp:/dev/sdq

how to make tier like service?, it’s because when my computer restart, tier device is gone, same with data in mount directory that i use to mount tier device,

Thank you

I moved this thread to the mailing list, if it’s OK for you.

There now is a mailing list available for tier : tier-users@lists.sourceforge.net

EPRD stands for eventually persistent ram disk.
This means that at some point data will be written to disk. However should the system crash or not cleanly shutdown then you will loose data.

When you use a modern filesystem like ext4 or xfs with barriers enabled then the filesystem will in most cases recover. As long as EPRD barrier support is also enabled. Since ext2 does not support barriers you can set the flush interval (-m) at a low value to prevent EPRD from loosing to much data after an unclean shutdown.

The trade-off is speed versus the chance of loosing data.

TIER is not like EPRD.
TIER is persistent. In the same way that the kernel loop driver is persistent.
The idea behind TIER is that you create multiple redundant (raid) storage layers. TIER will for example allow you to create a device that uses SSD + SAS + a file on NFS. TIER works with block devices and / or files.

Random IO will automatically be stored on the SSD device. While sequential IO will be written to SAS. Data that is not frequently access will eventually move to the file on NFS.

TIER divides the blockdevice in 1MB chunks stores metadata about their access patterns.

struct blockinfo {
unsigned int device;
u64 offset;
time_t lastused;
unsigned int readcount;
unsigned int writecount;
} __attribute__ ((packed));

You can change the data migration policy via sysfs.

I have some questions not exactly about this post, but EPRD vs. Tier.
Is there a mailing list available?

Currently there are very basic questions.
Is EPRD a non-persistent cache? If there is a power or disk failure what happens to the data? Is it going to be inconsistent?
I can read in the description that “disk cache with barrier support”.

Is Tier a persistent component of a “volume” created by the HDD and a fast device (ssd) and data moved into the fast device? How can I remove a tiered device?

Is there a comparison of the two technologies including functional and performance?

Thanks so much in advance for your answers and thanks for your hard work!

tamas

Did you check what test.sh actually does?
You may want to alter some things in this script.

Also make sure you only use -c with tier_setup only once if you don’t want to loose all data on the device.

i have downloaded tier.0.4.3, but i can’t set this up, when i try to run ./test.sh appear this error message :
insmod: error inserting ‘./tier.ko': -1 Invalid module format
rm: cannot remove `/data/ssd.img': No such file or directory
rm: cannot remove `/data/sas.img': No such file or directory
dd: opening `/data/ssd.img': No such file or directory
dd: opening `/data/sas.img': No such file or directory
./test.sh: line 10: ./tier_setup: cannot execute binary file

please give me some advice to fix this probelem
Thank you,

Regards,
Haferush

this is great, i still on research about optimizing cloud storage using tiering storage method, then i found your post, where i can download your tier software?

Regards
M. Aditya Haferush