Hi,
In this context it might be good to read Dave Hitz' Blog entry on RAID-DP and "overhead"...: http://blogs.netapp.com/dave/TechTalk/?permalink=Why-Double-Protecting-R AID-RAID-DP-Doesnt-Waste-Extra-Disk-Space.html
Enjoy!
Met vriendelijke groet / With kind regards, ___________________________________________
Geert van Teylingen System Engineer Network Appliance B.V.
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-----Original Message----- From: Bokkelkamp, Ernst [mailto:ernst.bokkelkamp@siemens.com] Sent: Monday, July 31, 2006 08:30 To: margesimpson@hushmail.com; toasters@mathworks.com Subject: RE: Storage space overheads!
"I wish NetApp had Raid5, this could have eliminated some issues like using 2 dual-parity drives."
Why ?
Somehow I get the impression, looking at the last few messages, that the majority does not understand raid_dp and the differences to raid_4. For practical purposes raid5 + some filesystem is "like" raid4 + wafl, particulary when you compare the data : parity disk ratio. Comparing raid4 to raid_dp you should notice that raid_dp provides a better protection with equal overhead when used on large volumes/aggregates. Large aggregates use the same number of parity disks but the raid_dp parity disks protect twice as many data disks compared to raid4. Sometimes the cost of one drive can be justified to provide additional protection on small volumes/aggregates, if not than you can always use raid4 instead.
Btw: there is an interesting document on WAFL in the knowledgebase - it is definitely worthwile to understand the principles behind WAFL to understand the benefits of raid4 and raid_dp.
Ernie
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of margesimpson@hushmail.com Sent: Montag, 31. Juli 2006 02:19 To: toasters@mathworks.com Subject: RE: Storage space overheads!
Hi all, Thank you very much. It seems out of 100GB, what usable space I can have is 55GB (55%). I feel yauk! But it seems at this point of time, its the only solution. I wish NetApp had Raid5, this could have eliminated some issues like using 2 dual-parity drives. Thank you again for your responses about SATA and FC disks.
Cheers, Marge.
On Fri, 28 Jul 2006 19:19:08 +1000 "Holland, William L" HollandWL@state.gov wrote:
We have a R200 which has 168 ATA drives. I expected a high failure rate on these as ATA drives are not rated for continuous
duty. I have
been surprised, and pleased, that failure rate has been very low - perhaps 3 drives in a year. Not sure about the SATA. The way I am moving is to use (S)ATA for my NAS (user shares) and FC drives for hosting my iSCSI LUNs. Databases need the higher performance of FC, simple file shares do not.
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner- toasters@mathworks.com] On Behalf Of margesimpson@hushmail.com Sent: Thursday, July 27, 2006 10:00 PM To: toasters@mathworks.com Subject: RE: Storage space overheads!
Hi Glenn D, Glenn W, Andrew, Michael, Holland and Holland,
Thank you
all for your feeback.
To summarize, the following is true (i.e., about storage sacrifice):
- Disk are right sized (realigning size in blocks from different
vendors...eg., for 72GB we get 68GB) before using by NetApp.
- dual parity (2 disks on RG of 16 => 14D+2P)
- spare disk/s
- WAFL & RAID overhead (~ 5%).
- aggr reserve 5% default
- vol snapshot reserve 20% default
- for LUNs: 50% for base snapshot + extra space 20% of remaining
data
space
- user data should always be below 90% to avoid performance
bottleneck
and defrag issues.
That's sounds bad to me, but if you all feel to be true then
its must
be a solution.
How about putting SATA disks on the primary filers to save costs? Whats are the problems in replacing FC disks with SATA? Whats record about SATA disks, I heard they are terrible? (Failure
rates is abnormal)
Thanks again for feedback. Marge.
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van Teylingen, Geert