RAID with SSD and traditional HD

nTia89 · 2014-08-07 08:30:16

Hi to everybody,

I've recently bought an SSD.
Now, my question is: it makes sense use my old HD (it's a notebook tradional hd, 5400rpm and 250GB) with my new SSD (hyperx 120GB) in an hardware RAID?

Awebb · 2014-08-07 08:37:10

According to most articles I have read so far about that topic, the only gain would be an increased sequencial reading. The other benefits should be negated by the raid not letting the SSD do its job. Just search the crawler of your choice for "ssd and raid" to find many articles about that topic.

nTia89 · 2014-08-07 08:46:26

that mad idea was born due to space limitation of SSD, so I'll setup a RAID 0 getting a logic volume with 2*120=240GB.
as I can read, RAID 0 boosts both reading and writing performance because the global workload is divided over the two hd. this is true if the hds are identical

in my case hds are different, so I'm worry about a decrease of performance between the RAID 0 solution and the SSD alone

mich41 · 2014-08-07 08:54:41

I don't think this will work well. Some pretty random 50% part of all IO operations will end up being serviced by the HDD and these operations will be sloooow.

nTia89 · 2014-08-07 08:57:15

ok!

but I think, performance of that RAID 0 will be anyway greater than HD only

frostschutz · 2014-08-07 11:10:38

I have a RAID-1 on my SSD. By default it has only one drive, so it's really just the SSD with 100% SSD performance.

But since it's a RAID-1, I can from time to time, add a HDD to it. With the HDD in --write-mostly mode, you get SSD read performance and HDD write performance.

That way the entire SSD content is mirrored to the HDD while the system is running. As soon as the sync is finished the HDD is removed from the RAID and you have a consistent/bootable mirror backup of your single SSD.

If your intention is not mirroring/backing up your SSD; but speeding up the HDD. You might want to look at bcache and similar mechanisms that were designed for the speed up task. In RAID-0 the HDD would slow down the SSD completely.

Personally I don't use those. Instead I partitioned my system so that everything is on SSD, but only the big clunky stuff that I don't mind being slow is on HDD.

That works very well for me; even though my SSD is small (only 64G) it's more than enough room for my system, home, configs, years of mails, coding projects, ... whereas movies and such are fine on HDD, they wouldn't play any faster if put or cached on SSD.

nTia89 · 2014-08-07 22:29:18

Thanks for the tips guys, I'll investigate on various solution and in the future I'll try it on my bare machine.

Ashren · 2014-08-07 22:37:44

Not really what you are asking for, but the new lvm cache feature is pretty nifty.

See here: http://rwmj.wordpress.com/2014/05/22/us … e-feature/

nTia89 · 2014-08-12 12:32:53

Due to an hardware failure I can't no more build a RAID

https://bbs.archlinux.org/viewtopic.php?id=185577

Arch Linux

#1 2014-08-07 08:30:16

RAID with SSD and traditional HD

#2 2014-08-07 08:37:10

Re: RAID with SSD and traditional HD

#3 2014-08-07 08:46:26

Re: RAID with SSD and traditional HD

#4 2014-08-07 08:54:41

Re: RAID with SSD and traditional HD

#5 2014-08-07 08:57:15

Re: RAID with SSD and traditional HD

#6 2014-08-07 11:10:38

Re: RAID with SSD and traditional HD

#7 2014-08-07 22:29:18

Re: RAID with SSD and traditional HD

#8 2014-08-07 22:37:44

Re: RAID with SSD and traditional HD

#9 2014-08-12 12:32:53

Re: RAID with SSD and traditional HD

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