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

fre 2006-06-09 klockan 14:45 -0400 skrev Robert Borkowski:

> 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

Technically RAID0 (striping) is not a RAID level, and additionally it
does not provide any benefits for Squid as Squid already distributes the
load on the available drives, so for Squid you only get the drawbacks..
(single drive failure invalidates the whole set..)

> 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.

A Squid setup using RAID1 should use a number of RAID1 drives.. no
reason to complicate matters by adding a RAID0 ontop of them..

> 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.

And random writes which is what RAID5 sucks worst at is what Squid needs
most..

but as long as the I/O load is within the limits RAID5 is often an
excellent tradeoff, especially if availability is more important than
performance.

> 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.

Is there any RAID controller hard or software which does not provide
spares and automatic rebuild?

> 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.

It depends a bit on the advice below..

> One thing you may consider is instead of one big squid server, build
> more smaller servers and load balance them.

Highly recommended!

Regards
Henrik