[mythtv-users] OT: Get off my SSD?!

[Dave Richardson]

> It's worth looking at just how much writing is going on. Even if all
> those blinks are writes (as already suggested they might be reads), it
> may be a trivial amount of data being written. I don't know the specs
> for your drive, but for the Intel drives, IIRC they say 20GB writes
> per day will give you a minimum 5 year life. If all your writes amount
> to nothing more than 1GB per day, then you could could reasonably
> concluded your writes are insignificant to the life of the drive (your
> write life will be 100 years....you'll discard the drive long before
> it would wear out). Again, that's for the intel drive...you'll need to
> find the rating for your drive.
>
> You can get the stats of your disk by running cat /prod/diskstats.
> When I do so, I get the following output (along with some other
> irrelevant lines for ram and loop devices):
> 8    0 sda 1987369 109134 159093252 9925928 13279357 9901152 456536514
> 754281540 0 39602364 766224960
> 8    1 sda1 941968 69129 23277467 6688764 12327909 9863153 177983344
> 739389312 0 27904536 748097548
> 8    2 sda2 1045333 39457 135815169 3236324 951448 37999 278553170
> 14892228 0 12502708 18126564
> 8    3 sda3 32 258 290 360 0 0 0 0 0 280 360
> 8   16 sdb 3556876 398622 588801245 10811168 1759825 11427 543315308
> 20747024 0 22980656 31552160
> 8   17 sdb1 3556857 398604 588800949 10811088 1759825 11427 543315308
> 20747024 0 22980540 31552052
>
> There you can see the stats of reads and writes for each drive (or
> even individual partitions). Here are the meaning of the fields
> (not...the number below don't count the first 3 columns, which are
> major/minor device number, and device name
> Field 1 -- # of reads issued
> Field 2 -- # of reads merged, field 6 -- # of writes merged
> Field 3 -- # of sectors read
> Field 4 -- # of milliseconds spent reading
> Field 5 -- # of writes completed
> Field 7 -- # of sectors written
> Field 8 -- # of milliseconds spent writing
> Field 9 -- # of I/Os currently in progress
> Field 10 -- # of milliseconds spent doing I/Os
> Field 11 -- weighted # of milliseconds spent doing I/Os
>
> The important field is 7...number of sectors. Multiply that by 512 to
> get the number of bytes written since last boot. So from this, I can
> see that sda has written 456536514*512/1024/1024/1024  -> 217GB of
> data since bootup. With an uptime of 28.5 days, that comes to 7.6GB
> per day.
>
> If I were to look at partition sda1, I can see that it's 1.3GB per
> day. That is the main partition for my master backend. It has the
> entire OS, mysql database, logging, and everything else except video
> and music files. Heck, it also contains the file systems for 2
> diskless frontends (including their logging). At that rate, I'd have
> no concerns putting that partition on an SSD with a write life similar
> to an intel SSD. And again, that's the master backend+2 frontends. I'd
> expect a single frontend machines to be way below that.
>
> So check these stats on your SSD drive and you may find it to be a
> trivial number of writes compared to your drive's lifetime wear
> rating.
>
> About the swap file, how much ram do you have? I've run diskless
> frontends with 1GB and 2GB of memory and never had a problem with no
> swap file.
>
>
> --
> Ron
> Ronald Frazier Photography - http://www.ronfphoto.com/
> Blogging About Photography - http://ronfrazier.blogspot.com/
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>

Thanks Ron, that's great feedback.
I have 4GB of RAM, ~ 3GB after nvidia tmpfs take pieces

I wasn't brave enough to go diskless for my first dedicated FE, that's
next.  I wanted a no-BS combination and had a few extra bucks.