Re: [vox-tech] RAID systems
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Re: [vox-tech] RAID systems
--- Bill Broadley <email@example.com> wrote:
> > > Measuring a real world workload in real world conditions. Short
> > > of that I'd recommend bonnie++ and "PostMark: A New File System
> > > Benchmark"
> > Right now all I have been doing is cron'ing iostat to give me
> > every few minutes.
> Very reasonable. Although thats a snapshot. iostat 60 or iostat 600
> will give you a more complete picture (24/7 totals instead of
Again, thanks for the great tip.
> > Yea, the worst is always what I plan for with these sorts of
> > but I guess no system is foolproof or failsafe.
> Indeed, but offsite offline backups are a great place to start.
I'll be talking to my boss about this today.
> > The best idea I have of the population of files that will be stored
> > random. I have general statistics, but they can change on even a
> > daily basis. Most of the storage would be for millions of <64k
> > files, but not always.
> I like to run something like:
> [root@localhost perl]# time ./dirstat.pl /
> scanning /
> Total directories = 25807
> Total files = 389283
> Total size = 98441.5 MB
> Average Directory = 15.1 files and 3906.08 KB
> Maximum Directory = 7522 files //dev
> Average filesize = 258.95 KB
> real 0m21.077s
> user 0m5.128s
> sys 0m10.775s
> [root@localhost perl]#
> So things to look for:
> * large directories might need application changes for smaller dirs,
> ext3 htrees, reiserfs or other support for large dirs.
> * average file size (for inode allocation)
Pretty handy little tool there.
> > > I believe ext3 will allocate additional inodes as needed, no need
> > > preallocate.
> > >
> > One of the previous raid systems (scsi hardware raid) that we had
> > out of inodes (it was formatted ufs and ran in solaris) in the
> > month or two that we used it for production. I just don't want to
> > the same mistake twice...
> Ugh, indeed, I must have misremember or maybe remembering for the
> filesystem. Never allocate more than one inode per block though,
> they will go to waste.
> > As mentioned before, pretty randomized populations, and there's a
> > degree of variance between projects. Basically, we are sent huge
> > populations of data, we process the data into different formats,
> > return it. The input data are mostly correspondance (email, word
> > spreadsheets, etc), but that is generally just a rule of thumb...
> > populations are simply moving targets that vary widely from each
> > project, and that is all that I have to go on... :)
> If you are ever stuck with a lack of inodes you can make a filesystem
> in a
> file and loop mount it.
Just make sure that you have one free inode to make the file...
> > For some projects, there can be 3 million files where 99% are less
> > 4k in size. For others there can be 3000 files where all are more
> mkfs.ext3 -T news will make one inode per 4kb block.
Exactly the option I used, I must have forgotten to post that.
Actually, as i recall, it was:
[root@localhost /]# mkfs.ext3 -b 4096 -R stride=16 -T news /dev/md0
> > 128k. Most fall somewhere in between. Knowing exact numbers would
> > mean that I could tell the future and know what would be coming in
> > door (which would be cool...).
> > Again, here is my dilemma. I just chose something that would
> > e "good enough(tm)" to use everyday, and something that would
> handle 30
> > gazillion 2k files (I for-sure know there will be gazillions of
> > most of which are less than 2k, what I don't know is the ratio of
> > smaller files to larger files).
> Files smaller than blocksize aren't coalesced afaik, you might need
> another fs if you need it, on the otherhand you can set 1k or 2k
For some cases, I might think about reducing the block size, but for
now, I am just going to sit with 4k blocks until there is a good reason
to move to a smaller size. Even before I think of reducing block
sizes, I might think about trying reiserfs if the performance for
small files isn't great. I might be building a few more of these boxes
soon, so that is one thing I am still going to try out. I think I'll
try it out just to get a comparison between the two fs's.
> > I have a triple supply on the drive cabinet and a double supply on
> > box, all fed by UPS.
Thanks for all the help and advice, Bill. I humbly bow to your wise
> Bill Broadley
> Computational Science and Engineering
> UC Davis
> vox-tech mailing list
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