On Wed, 31 Dec 2014 10:14, Per Jessen wrote:

jdd wrote:

...

Hello, I wonder if it could be a good idea to make a raid with a ssd and an hdd together (mirror).

will the hdd kill the ssd speed advantage or do the ssd boost the hole raid?

Assuming we're talking about mdraid, my immediate thought - on read, you might get some ssd boost, but on write I don't see any.

Correct, not to mention that genuine hybrid-drives are much better optimised than any raid of ssd+hdd. Spare yourself that headache. It gets even worse in 'hardware' raid controllers, there even the read preformace can drop to hdd levels b/c of 'wait-for-other-disk' to verify the data. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

jdd wrote:

Le 31/12/2014 10:14, Per Jessen a écrit :

...

Assuming we're talking about mdraid, my immediate thought - on read, you might get some ssd boost, but on write I don't see any.

yes, but read are what is the most frequent :-)

If that is the case, I guess a hdd+ssd raid might bring some improvement. Depending on the read/write ratio and the system memory, just adding more memory might bring the same though.

I wondered that because bcache seems to be some sort of mixed raid. May be better than normal raid.

AFAIK, bcache is essentially an extended file system cache. It just adds a level of very fast and very large cache. I don't see any RAID-like functionality in that. -- Per Jessen, Zürich (0.8°C) http://www.dns24.ch/ - free dynamic DNS, made in Switzerland. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

On 2014-12-31 14:34, jdd wrote:

Le 31/12/2014 12:08, Per Jessen a écrit :

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AFAIK, bcache is essentially an extended file system cache. It just adds a level of very fast and very large cache. I don't see any RAID-like functionality in that.

as far as I understand, one needs to make two equal sized partition, one caching the other

No, with bcache the ssd space is way smaller. -- Cheers / Saludos, Carlos E. R. (from 13.1 x86_64 "Bottle" at Telcontar)

Le 31/12/2014 18:08, Malcolm a écrit :

On my two setups I used a size of 10% of the rotating rust, seems to work fine in my tests. I image it can be smaller, but I guess dependent of files size and throughput would determine.

reading your data in the other mail, I don't understand it. wich disk is the ssd? NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 111.8G 0 disk ├─sda1 8:1 0 260M 0 part /boot/efi ├─sda2 8:2 0 73.7G 0 part / ├─sda3 8:3 0 8G 0 part [SWAP] is sda the ssd? └─sda4 8:4 0 29.8G 0 part └─bcache0 253:0 0 298.1G 0 disk /data sdb 8:16 0 298.1G 0 disk └─sdb1 8:17 0 298.1G 0 part └─bcache0 253:0 0 298.1G 0 disk /data if so it's very interesting for me. I have 100Gb spare on my last (and faster) ssd and 500Gb data on my old 1Tb rotating disk (all this on my main station, not the laptop) I have to reread the bcache doc, thanks jdd -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

Le 31/12/2014 18:28, Malcolm a écrit :

Correct sda is the ssd and the caching device is sda4 the backing device is sdb1, sda4 is 10% of the sdb1 device (a 320GB hdd). https://forums.opensuse.org/entry.php/159-Setting-up-bcache-on-openSUSE-13-2 I use a script to test before and after with both the ssd and the hdd and then bcache0 it uses the fio tool... aplied, will see the result.

The main thing I didn't understand is that the two bcache devices (caching and backup) do not need to have the same size. shame also it can't be applied to /root, I do very litle data management on my laptop :-( thanks jdd -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

Le 31/12/2014 18:05, Malcolm a écrit :

Use bcache...... in this laptop I have an SSD and a HDD;

yes. On an other computer I have a small (32Gb) ssd included and I plan to use bcache, but the config is not that clear

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 111.8G 0 disk ├─sda1 8:1 0 260M 0 part /boot/efi ├─sda2 8:2 0 73.7G 0 part / ├─sda3 8:3 0 8G 0 part [SWAP] └─sda4 8:4 0 29.8G 0 part └─bcache0 253:0 0 298.1G 0 disk /data sdb 8:16 0 298.1G 0 disk └─sdb1 8:17 0 298.1G 0 part └─bcache0 253:0 0 298.1G 0 disk /data

I believe there are issues if you suspend or hibernate, I don't use it, so not sure of the effect...

If I can forbid this (hibernate), i don't like it (uses battery, not that faster than a boot) but If I read well your datas, bcache uses twice the disk size (sda4 and sdb1)? is it not easier to install the distro directly on the ssd? I could see an interest if the cache was much smaller than the disk thanks jdd -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

Le 31/12/2014 18:55, Felix Miata a écrit :

jdd composed on 2014-12-31 18:13 (UTC+0100):

...

If I can forbid this (hibernate), i don't like it (uses battery, not that faster than a boot)

To prevent it from happening, have you tried the things on

not yet tested, but I keep your mail to read soon, thanks jdd -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org