32GB of SSD, how to use?

[user5031858]

Hi there,
I have got ASUS UX32VD ultrabook, it is equipped with 500GB ordinary HDD and 32GB of SSD (mSATA) which is used in original windows configuration as invisible cache over the ordinary HDD (accumulates frequently accessed data).

I wounder how can I get maximum from this free add-on, I have the following options (more than one may apply I guess):
1. Put swap partition on this drive (doesn't it kill my SSD very quickly?)
2. Put /boot on this drive
3. Tune somehow to hibernate on this drive
4. Put system files (those heavily used during boot and Gnome start up), unfortunately I do not know how what is the best equivalent of C:\windows on linux
5. Use LVM, split SSD on 4-8 physical volumes, split HDD on N physical volumes, then mix them into logical volume groups as needed (trying to put maximum of system files on SSD and if not fit enlarge the space with physical volumes from HDD)
6. Use SSD as temporary storage for some operations that require fast filesystem (build scripts, image processing, etc.)

[stevea]

This should give you a starting point for SSD under Linux.
first http://forums.fedoraforum.org/showthread.php?t=277082

Originally Posted by user5031858

...
how can I get maximum from this free add-on, I have the following options (more than one may apply I guess):
1. Put swap partition on this drive (doesn't it kill my SSD very quickly?)
2. Put /boot on this drive
3. Tune somehow to hibernate on this drive
4. Put system files (those heavily used during boot and Gnome start up), unfortunately I do not know how what is the best equivalent of C:\windows on linux
5. Use LVM, split SSD on 4-8 physical volumes, split HDD on N physical volumes, then mix them into logical volume groups as needed (trying to put maximum of system files on SSD and if not fit enlarge the space with physical volumes from HDD)
6. Use SSD as temporary storage for some operations that require fast filesystem (build scripts, image processing, etc.)

1/ Not likely. If you are swapping a lot this would help, but if you are swapping a lot you should just buy more dram - even swapping to SSD will be ugly.
2/ No. Boot could go there- but the advantage of SSD is the brilliant access times and you only access boot once per system-session. Save a few seconds once but no impact on the workload.
3/ Maybe. You can hibernate there and it does make hibernate/restore a lot faster. To do this you need to set aside DRAM size swap (you can have multiple swaps) so then you may as well use the '1/' strategy. Depends on how often you hibernate. whether this makes sense.
4/ Yes - reasonable and C:/ is roughly the root '/' partition minus /home and /opt. You'd want to diddle the bootloader to use the SSD parttion as the root I think.
5/ NO ! NO! NO! LVM is too crude a tool. It doesn't balance load based on fast/slow disks. It only balances on a geometry basis. This would effectively throw the SSD advantages away. I do NOT recommend LVM for most users/and-laptops. It's good features are nearly useless there, but it does impose a performance penalty.
6/ YES - but how.

More to follow ...

[george_toolan]

A 32 GiB SSD should be large enough to install the whole operation system and still leave some room for a 16 GiB swap file. Not sure if Linux supports hibernating to a swap file, though.

6) Easy. Most programs use /tmp for temporary storage or at least you can configure where to put temporary files.

[user5031858]

Originally Posted by stevea

1/ Not likely. If you are swapping a lot this would help, but if you are swapping a lot you should just buy more dram - even swapping to SSD will be ugly.

Agree that RAM is better, but even in 10GB (maximum for this utrabook) configuration swapping may be required sometimes.
So the real question is:
is it worth spending some of this small SSD on swap partition (or it may be used better way)? If I had 10GB RAM I would certainly put swap on HDD because swapping would be rare event and it will just help the system to run somehow... But currently I have only 4GB (planning expansion to 6GB) so quick swap may be welcomed.
But currently I tends to idea that if swap goes to SSD it may wear off very quickly because of frequent write operations and will not help much in case of swapping (will be far slower than real RAM). Probably there might a better way to get advantage of SSD in every day use (system files, etc.)

---------- Post added at 02:18 PM ---------- Previous post was at 01:24 PM ----------

Originally Posted by stevea

5/ NO ! NO! NO! LVM is too crude a tool. It doesn't balance load based on fast/slow disks. It only balances on a geometry basis. This would effectively throw the SSD advantages away. I do NOT recommend LVM for most users/and-laptops. It's good features are nearly useless there, but it does impose a performance penalty.

if it were to mix SSD with equal in size HDD, I would agree with you. But if I planned to create say 2 LVG: "system" and "user", and by default give all SSD to system and some of huge HDD to user, then in case system volume will not fit into SSD I can add some space from HDD to system LVG -- of course newly added libraries might sit on HDD now, but I need not to reinstall the whole system. Makes sense? ( I can even move all system files to HDD in case my SSD will show first signs of wear, does it sound too optimistic?)

---------- Post added at 02:31 PM ---------- Previous post was at 02:18 PM ----------

Originally Posted by george_toolan

6) Easy. Most programs use /tmp for temporary storage or at least you can configure where to put temporary files.

even easier -- I use NetBeans, Eclipse, IBM Rational tools they all just a massive bunches of primarily read-only but small files (tonnes of JAR files), usually I install this stuff as user (not under root) so I can only mount this 32GB SSD for such usage... And if SSD will fail one day I will just reinstall this software to HDD and forget about this 32GB nuisance... While having /tmp or /var in the SSD is a bit more risky.

[stevea]

Originally Posted by george_toolan

... Not sure if Linux supports hibernating to a swap file, though.

6) Easy. Most programs use /tmp for temporary storage or at least you can configure where to put temporary files.

George. I see you SPECULATING and FUDing a lot when an answer is required.

Linux hibernates to swap - it's been that way since the 2.2 kernel. For this to work swap should be as large as dram.

/tmp is indeed used for SOME 'work' files, like compiler intermediates, but also for a lot of less dynamic uses. Browse to a video or a pdf file and you'll see the garbage remains in /tmp. I don't think it's real productive to put /tmp on SSD. If you do a lot of compiles and want the compile/cache on SSD, then just set CCACHE_DIR (see 'man ccache').

So /tmp isn't the main destination for working files that you might suspect.

Originally Posted by user5031858

Agree that RAM is better, but even in 10GB (maximum for this utrabook) configuration swapping may be required sometimes.

Don't know your intentions for use - but it takes a pretty harsh load to get far into swap w/ 10GB DRAM. BUT keep in mind that swap is still a big performance hit even on SSD. For a interactive systems (as opposed to a backroom server) use of swap means the interactivity is badly crippled. You'll certainly consider a swapping laptop as basically unusable except as a doorstop. I did an Andoid build (~3GB in the source tree) last week on my laptop (SSD, 8GB DRAM) and used "make -j" (a poor idea) to allow make to exec an arbitrary number of threads. This pushed about 3GB into SWAP, and i couldn't even move the cursor except erratically, basic screen tools like gkrellm would update once every minute or two. This continued for the ~30 minute build.

So the real question is:
is it worth spending some of this small SSD on swap partition (or it may be used better way)? If I had 10GB RAM I would certainly put swap on HDD because swapping would be rare event and it will just help the system to run somehow... But currently I have only 4GB (planning expansion to 6GB) so quick swap may be welcomed.
But currently I tends to idea that if swap goes to SSD it may wear off very quickly because of frequent write operations and will not help much in case of swapping (will be far slower than real RAM). Probably there might a better way to get advantage of SSD in every day use (system files, etc.)

IMO swapping performance is very awful in either case. Unless you really expect to swap often and accept that the system will be non-interactive until the swapping is done - then you really want to avoid heavy swapping at all costs. My approach would be to put Swap on the rotating disk, so long as I could generally avoid swapping.

Another approach is to take a SMALL amount of the tiny SSD (like 1GB) and set this up in addition to a full sized swap on rotating disk. In the fstab give the SSD swap higher priority (on the fstab options use pri=42 ), see the 'man swapon' page for details. This causes the SSD to be used preferentially for swap until it's 1GB is filled. IF you swap more than that, then the rotating disk swap is used.

=======


My actual approach to your dilemma would be to use one of the two 'SSD as cache approaches under Linux.

http://bcache.evilpiepirate.org/
http://git//evilpiepirate.org/~kent/linux-bcache.git
OR
https://github.com/facebook/flashcache/

[user5031858]

Originally Posted by stevea

4/ Yes - reasonable and C:/ is roughly the root '/' partition minus /home and /opt. You'd want to diddle the bootloader to use the SSD parttion as the root I think.

I think I need to put
/var/logs
/var/lock
/tmp
/var/tmp
on HDD, since they will wear off the SSD very quickly. There is only 3000 write cycles on SSD? I guess /tmp directory is updated very frequent...
Many programs install into /usr, will 32GB be enough?

[schotty]

Well, I use the SSD (64GB) for root and /boot, and the rest (swap, /home) go onto my spinning disk (1TB).

Granted its getting a little less use than I would normally prefer, but I am unwilling to do much more there, as the swap is likely to pound that SSD a bit too harshly, and although I would love to put /home there, I have too many games :P

[user5031858]

Originally Posted by stevea

My actual approach to your dilemma would be to use one of the two 'SSD as cache approaches under Linux.

http://bcache.evilpiepirate.org/
http://git//evilpiepirate.org/~kent/linux-bcache.git
OR
https://github.com/facebook/flashcache/

Thank you,
I will probably install on HDD now and decide which caching technology to use, later.
Using this as a cache is actually a good idea:
1. it was original idea of vendor
2. if this SSD will be ruined during heavy read/write usage, I will not cry
All this SSD-revolution makes me angry -- they propose products that are only quicker in read but equal or worse in other aspects of storage. I just wonder how cheaper my device might be if there were not SSD installed.

[Gareth Jones]

Personally I'd put / and /boot on the solid-state, and put /var, /home, /tmp and swap on the hard-disk. That gets you the benefit of fast boot and program starts, but keeps the larger space for files that are less frequently accessed or more frequently modified.

[jlpierce]

Originally Posted by user5031858

I think I need to put
/var/logs
/var/lock
/tmp
/var/tmp
on HDD, since they will wear off the SSD very quickly. There is only 3000 write cycles on SSD? I guess /tmp directory is updated very frequent...
Many programs install into /usr, will 32GB be enough?

I don't know where you got the 3,000 write cycles from, but you will not wear it out in a month or even 2 years. It may abruptly die because of electronic failure (capacitor or cell failure.)

As far as writes go, windows will abuse a drive just as much as any linux distribution will.

Just my opinion.

[george_toolan]

It is virtually impossible to kill a SSD just by writing to it. That's at least 3000 write cycles per cell, so with intelligent wear levelling you get about 3000 * 30 GiB = 90 TiB writes ;-)

Swapping to HDDs is totally useless. If you must swap then at least use a SSD if you have one. Gkrellm will show about 10k - 15k swap operations per second where a normal HDD only allows a couple of hundred.

[user5031858]

Originally Posted by jlpierce

I don't know where you got the 3,000 write cycles from

from this post: http://forums.fedoraforum.org/showpo...52&postcount=3
the friend of mine said his SSD (probably of early generations) was worn out very quickly, he used it in home-brewn media center (running on Windose though, and despite he undertook special measures to reduce write operations)

[george_toolan]

Actually earlier generations of flash memory cells allowed more write cycles.

Have a look at this article http://www.storagesearch.com/ssdmyths-endurance.html

According to his calculations a SSD would only last for about 51 years ;-)

[user5031858]

after all I found the most practical to mount this device as /mtn/fast while having system installed on the ususal drive.
created ~/eclipse and ~/workspace as links to this filesystem /mnt/fast/eclipse and /mnt/fast/workspace and put a development Web server there... and I guess this is the best usage pattern for me -- since I boot OS once a day -- and everything frequently used got in usual in-memory cache of HDD, while I do deploy and undeploy large Java artifacts on the server and develop them...

I decided not to install OS on this small SSD because with original BIOS/EFII SSD sometimes got invisible
After BIOS was flashed -- disk appeared to be stable and I had to think how to use and how to use it better...

So for people developing large artfacts I recommend this pattern: link "problematic" parts of your home directory to this "fast" device (under problematic I mean big heaps of small files that should be read fast)