Re: [squid-users] Squid in gigabit speed continuing...

> -----Original Message-----
> From: Pasi Pekka Leinonen [mailto:pasi-leinonen@suomi24.fi]
> Sent: June 9, 2006 1:01 PM
> To: squid-users@squid-cache.org
> Subject: [squid-users] Squid in gigabit speed continuing...
>
>
> Very big thanks to all who replied to my earlier message!
>
> If I understand right, RAID is bad on access time and if I want fast
> proxy I should buy e.g. WD Raptor 10000rpm.
>
> How does RAID slows down the disks speed if I have e.g. 4 pcs WD
> Raptor 10000rpm 74Gb on hardware or software RAID? Or is it realy
> better to have 4 pcs WD Raptor 10000rpm without RAID? Or is the gain
> from RAID so little it's not worth it?
>
> What would be the best amount of storage to cache 300 user network.
>
> which is most important when not using RAID: The amount of disk space
> or the amount of disks.
>
>
>

There are different types of RAID, each with different tradeoffs in read/write performance, reliability and disk space.
With four drives you could do:
RAID0 very fast reads/writes, very poor reliability (Lose one disk and you've lost EVERYTHING), four disks worth of space
RAID0+1 which gives you very good write speeds, can lose one drive, maybe even two depending on which ones go. Half the
drives are copies so you get half the disk space available.
RAID5 gives you good read speeds, relatively poor write speeds. Can lose any one drive. One drive's worth of data is
used for redundancy so you only get three drives of available space.

One more option some RAID controllers give you is automatic recovery. You have a fifth drive in the system that is kept
as a spare. When the controller detects a bad drive it rebuilds the information that was on the failed drive onto the spare.

Production squids here use RAID1 on two drives. Considering how failure prone hard drives are (We have at least one or
two failures per month) I wouldn't risk production systems to non-redundant storage, even at the cost of some performance.

One thing you may consider is instead of one big squid server, build more smaller servers and load balance them.
Check whether it's more cost effective to deal with four servers at 250Mbps, or one server at 1Gbps. Smaller servers
are typically much cheaper than Big Iron, and you gain the ability to add extra power in smaller, less painful chunks.

-- 
Robert Borkowski