Ext4 hacker Ted Ts'o converts his laptop [LWN.net]

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 1, 2008 7:23 UTC (Tue) by Camarade_Tux (guest, #51944)
In reply to: Ext4 hacker Ted Ts'o converts his laptop by Zorggy
Parent article: Ext4 hacker Ted Ts'o converts his laptop

I still don't get how people imagine everything is about to use SSDs. SSDs die after far less
write cycles than hard drives.
Quoting wikipedia : 
"Limited write cycles  flash-memory storage will often wear out after 300,000-500,000 write
cycles[citation needed]"
(but citations are easy to find)

This page seems to be a good reference : http://wiki.eeeuser.com/ssd_write_limit
Basically, it states eee user won't have problems. But well, eee users aren't server users or
even regular users.
Compile anything and you're damaging your hard drive (kernel, webkit). Download something
(let's say a Debian iso) and you're facing the same problem. Defragment your drives and you're
dead (vista does this on a regular basis by default). In fact, even the eee users may have
this problem if their browser flushes things to disk too frequently.
So, no, I don't think those are going to be mainstream soon or so I hope.

(and SSDs draw more power than regular hard drives atm :
http://www.tomshardware.com/reviews/ssd-hdd-battery,1955....)


Sorry for the off-topic but I couldn't stand any longer. ;)

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Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 1, 2008 9:11 UTC (Tue) by Zorggy (subscriber, #51397) [Link]

Of course I did not explained that SSD would replace disks next year, but it is a fast
evolving technology. The example you show is a bit biased as the EeePC is a very low-cost
computer, not integrating the cutting-edge technology, far more expensive.

But you are right, there are some limiting constraints that must be taken into account when
using a file-system. There are some specialized ones such as JFFS2, YAFFS, LogFS or UBIFS
which are far better when managing SSD compared to EXTx, specialized in rotating disks.

And about the consumption, I can read from the article you provided: "we received confirmation
from two vendors that many flash devices dont feature power saving mechanisms yet". That
could be a path for huge improvements in a near future.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 2, 2008 18:19 UTC (Wed) by oak (guest, #2786) [Link]

Regarding JFFS2, it scales *very* badly.  I think OLPC has done some work 
for it to be usable with 1/2GB partition sizes, but basically JFFS2 is 
obsolete technology with today's disk sizes.

I've heard that the larger SSD disks might support less write-cycles 
(there's more space over which to spread the writes so it could be less of 
an issue for normal desktop users), any idea whether this is true?

Swap is one use-case for disk with which SSD doesn't deal that well, I 
guess computers of future still need swap...

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 2, 2008 19:00 UTC (Wed) by martinfick (subscriber, #4455) [Link]

Swap is one use-case for disk with which SSD doesn't deal that well, I guess computers of future still need swap...

Uh, probably not. Why bother swapping to an expensive medium when swap does not need to be persistent, just add more RAM. You could even devise slower RAM based non persistent drives if you were worried about cost. Swap should die if spinning disks die. The whole point of swap is that in theory it is cheaper than RAM, not that is is persistent. Makes me wonder why no one is building a cheap non persistent "swap" drive yet, do they?

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 1, 2008 9:15 UTC (Tue) by rvfh (subscriber, #31018) [Link]

If you read papers from people like Sandisk, they basically say that current SSDs will outlast
your computer. It is not [virtually] illimited in write cycles as HD are, but it is enough for
a normal _desktop_ user.

And it will only get better...

And HDs die in other ways (I lost 5 so far at home, out of about 15)...

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 1, 2008 10:59 UTC (Tue) by endecotp (guest, #36428) [Link]

Like it says, CITATION NEEDED.

Magnetic disks fail too.  They've got moving parts in them!!!!!  Maybe you've never had a
magnetic disk fail, but I bet you know someone who has.

I've been using exclusively flash storage for a couple of years now and it has been very
reliable.  Yes, I compile things, download things and so on; in fact I spend most of my time
doing exactly that, on flash drives.  I have had one USB "thumb drive" fail, but it was a
cheap one and I don't believe it was anything related to the write limit; none of my IDE
drives or modules has ever had a problem.

As for the power consumption, I have found my drives to take at least an order of magnitude
less than magnetic disks.

The greatest benefit for me, however, is that they are silent.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 1, 2008 23:03 UTC (Tue) by k8to (subscriber, #15413) [Link]

Ugh, this useless old red herring.

The article shows that if your disk is under continuous writes of megabytes a second without
pause that it will still last for YEARS.

Some server deployments may be of this nature.  NO desktop deployments are.  If you like I
could monitor iostat data for my workstation that acts a s a fileserver, does bittorrent
periodically, on which I compile software, and develop software and so on.  I can assure you
that the disks are idle over 80% of the time.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 2, 2008 2:52 UTC (Wed) by jwb (guest, #15467) [Link]

Obviously you've never used tracker ;)

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 3, 2008 22:36 UTC (Thu) by liljencrantz (subscriber, #28458) [Link]

Under regular load, 90 % of the IO done by tracker is reading. When tracker hangs and keeps
rereading the same file over and over, 100 % of the io is reading. SSDs can handle it just
fine.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 2, 2008 9:21 UTC (Wed) by drag (subscriber, #31333) [Link]

Well traditional harddrives have write limits also. And, like any computer person, have had
more then one harddrive fail prematurely.

And, more importantly for the direction that PCs are going.. when you drop your laptop on it's
corner you won't crash the read heads on a solid state disk. 

AND, SSDs for most purposes are much much faster. Low seek times, you see.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 2, 2008 19:27 UTC (Wed) by nix (subscriber, #2304) [Link]

But the write times are lousy. Really, really lousy.

Ext4 hacker Ted Ts'o converts his laptop

Posted Jul 3, 2008 22:39 UTC (Thu) by jwb (guest, #15467) [Link]

The flash SSD market is very segmented.  A lot of the disk-form-factor stuff out there has
mediocre performance.  However there is a company with a product on the market that's about
100-200x faster than disk on both reads and writes, both random and sequential, and especially
on mixed read/write loads.  The pricing is about $25/GB which isn't all that bad when you
break it down.

Speaking about laptops

Posted Jul 2, 2008 6:37 UTC (Wed) by man_ls (subscriber, #15091) [Link]

The article on Tom's Hardware says that power consumption of a high-end SSD disk can be worse than for a 2.5" high-end laptop disk; but the comparison cannot be generalized. It only compares disks with very high performance and steep prices. Cheaper, slower SSD drives may easily draw less power, and they even benchmark a Sandisk unit that shows it.

OTOH 3.5" disks, which have different constraints as to power and energy savings, will draw quite more power (a quick Google search shows peak consumption of 6-13W, instead of 2-4W for 2.5" disks). Meanwhile an SSD disk has the same basic consumption, be it 3.5" or 1.8", as the article shows. So there is a lot of potential savings even in the high end.