Re: SATA 3ware RAID review...sort of.
From: Gerald (gcoon_at_inch.com)
Date: 02/05/05
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Date: Fri, 4 Feb 2005 18:38:48 -0500 (EST) To: Simon <simon@optinet.com>
On Fri, 4 Feb 2005, Simon wrote:
> While your review is helpful, I hope you realize that server's throughput doesn't
> indicate the load you are putting on the card or the harddrives. If you were
> serving large movie files, you could quickly fill up both of your 100mbps links
> with a single 5.4k RPM ATA drve, given you have some RAM so FreeBSD
> could cache the data being served. 30Mbps of bandwidth is merely ~3mBps
> of sustained disk transfer. Most of this data could be cached by FreeBSD
> without you even knowing. It could also be cached by the memory on the
> control and harddrives.
Quite a bit of the drive is being cached in memory. Between Apache and
the OS the memory is being put to good use, but I just wanted to send
out that the SATA setup is standing up to my commercial load for this
particular customer.
> What would be very useful is if you could mention what kind of files are being
> served (their size), how many hits the server serves every second. Are they
> mostly the same files or completely random, and so on... how often is the server
> writing to disk, is it creating many random files? how big? how often? there is
> just so many things involved, you can't merely post your hardware and say you
> are pushing 30mbps of bandwidth. I have a 8x250gb using PATA and 3ware
> 8port 8600 series card which can do sustained reads of over 100mBps which
> would translate into ~1000mbps of bandwidth. However, this doesn't indicate
> that it would be able to serve 50,000,000 small, mostly random files, a day like
> a similar server using SCSI could. Don't forget, it's one thing when you just
> read, but completely different when you read and write, especially with RAID5.
Granted and I tried to write enough disclaimers to cover all that. In
talking to some other admins I'm most interested to see the following:
1. Backups (working on adding snapshots to dump/amanda now)
2. Reads + Writes. I think there's only 2 occasions when a lot of writes
are made to the disks. ...but it's a web server. There's supposed to be
more reads than writes. I would hope someone reading my E-mail would
be able to easily discern all of what you have correctly pointed out.
Nothing is ever simple and I hope my E-mail didn't came across as an
attempt to oversimplify a complex operating system and application.
Top has this:
Mem: 840M Active, 2452M Inact, 270M Wired, 189M Cache, 112M Buf, 138M Free
Systat has this:
Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER
Tot Share Tot Share Free in out in out
Act 163180 6012 816892 11436 290788 count 57
All 3884364 8132 2855508 15612 pages 279
Interrupts
Proc:r p d s w Csw Trp Sys Int Sof Flt 170 cow 1998 total
397 5390 1932 5340 3397 667 1538 275352 wire 6: fdc0
873736 act 128 8: rtc
19.0%Sys 3.6%Intr 19.0%User 0.0%Nice 58.4%Idl 2542712 inact 13: npx
| | | | | | | | | | 202748 cache 15: ata
=========++>>>>>>>>>> 88040 free 1704 28: em0
daefr 66 48: twa
Namei Name-cache Dir-cache 2079 prcfr 100 0: clk
Calls hits % hits % 78 react
5891 5847 99 13 0 pdwake
1193 zfod pdpgs
Disks da0 pass0 1193 ofod intrn
KB/t 17.59 0.00 %slo-z 114880 buf
tps 65 0 2156 tfree 41 dirtybuf
MB/s 1.12 0.00 100000 desiredvnodes
% busy 38 0 90784 numvnodes
4716 freevnodes
The OS is caching between 2.5 and 3 GB of I/O. As far as file sizes and
getting in to really small details I have a lot of work left to do on
this server to go in to too much. It's a public web server though so go
to www.firstview.com and answer some of those questions yourself. Just
trying to contribute what I can. (Disclaimer since it seems to be asked
often when I give that link: neither I nor my company designed the web
site.)
Gerald
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- Previous message: Simon: "Re: SATA 3ware RAID review...sort of."
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