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This topic comprises 2 pages: 1 2
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Author
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Topic: Dolby DSS220/pricing
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Brad Miller
Administrator
Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99
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posted 08-25-2011 12:01 AM
Mark, you keep missing my point. That 5% you speak of is when the disk read/write is getting its workout. That is when the 3 drive raid isn't as efficient. That is the only time I have ever seen playback problems. I am concerned with one thing, uptime!
We can debate this until your fingers fall off, but the fact remains 3 drive raids are NOT as solid as 4 drive raids. Software raids are also NOT as solid as hardware raids. Any server with only one non-raided OS drive is built to fail. There it is, I said it. It may not fail for a few years, but every SATA drive dies. Since it's pretty obvious we are speaking of GDC, they told me when that drive dies the server is down, as it stores critical media block info on it. This was as recent as a month or two ago. Has something changed VERY recently? I spoke with them about raid'ing that OS drive and adding a 4th drive to their content raid and they are working on that (as well as other things) in a future server release...which is a thumbs up to GDC once it happens.
Keep in mind I'm also not targeting GDC. Doremi has 2 models, the DCP2000 and DCP2K4. I would not recommend anyone buy the DCP2000 because of that 3 drive raid. (All of Doremi's servers are software raid like GDC, so that isn't an option.) However Doremi's DCP2K4 unit has a 4 drive raid. That's the one to get. At that point the only thing you are stuck with is when those flash chips die. I have seen a 25% failure rate. Still though that is better than the guaranteed 100% failure rate of a GDC when the OS SATA drive dies.
I'm not letting Dolby off easy here either though. Dolby is about to introduce 2 new models for IMBs. One has that silly 3 drive raid in it, the other I believe is a 5 drive raid. You won't find me saying anything nice about their 3 drive raid model, so don't think for a second this is a brand issue. This is a hardware, design and performance issue.
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 08-25-2011 03:57 AM
There was a time when Doremi had an issue with a single type of flash disk, and they went over to a different type. Now with the USB backup/restore mechanism, they are the easiest to get back on line.
If there was a 25% failure rate, they would be out of the business already.
There might be a difference between smaller houses with local technicians and larger plexes with NOC. It seems obvious that Dolby has a history of many failed drives, but a failed drive doesn't mean downtime if managed properly.
I really don't see a difference between hardware and software raids nowadys - technically, this difference doesn't exist. Hardware raid is software as well, and battery buffering is only used on a small part of dedicated controllers - could be solved by a server USV just as well, and raid controller buffering doesn't mean a file system is consistent after a power failure - the file system is still runnng on the OS, not the RAID controller.
That said, Sony currently is the only one with dual-drive redundancy (RAID6).
To me, the Doremi 2k4 approach with a write protected Flash and a 3+1 RAID seems favourable. RAID controllers need to be second sourced, it could be very complicated nowadays to ensure supply in the long run, since product cycles are so short. I always try to avoid to be dependant on a specialized piece of hardware.
You can always move a software RAID to a different machine if it uses open block building/standard parameters.
- Carsten
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Terrence Meiczinger
Film Handler
Posts: 45
From: Orono, Me, USA
Registered: Dec 2008
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posted 08-26-2011 01:09 AM
I'm probably missing something, but why would a 3 drive RAID suck and a 5 drive RAID array necessarily be better?
If it is RAID 5, regardless of the number of drives, the array can only withstand one drive failure. Increasing the number of drives in a RAID 5 mathematically increases the array failure rate. Now, if the individual drives are larger in the 3 drive array to achieve the same storage, that could cause a slight disadvantage because it will take longer to rebuild increasing the window of a second failure. As for read performance, there is some gain (depending on the data access) from more drives in a healthy array, but in a degraded state, the more drives the slower it will be since it has to read the parity data off each drive. In this case, the minimum of 3 drives would yield the best performance.
If the 5 drive system was RAID 6, then sure, it would have the added advantage of being able to survive two drive failures. However, the performance degradation of RAID 6, especially when writing can be brutal. You want the added safety on your show library, but it probably isn't worth it on the digital server. The better solution would be a nested array, such as 1+0.
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 08-26-2011 07:38 AM
Terrence - you are right that the type of RAID config makes the difference, not the number of drives directly. However, some servers allow to have a backup drive inserted all the time. So, if like on the Dolby servers, RAID repair can happen automatically, a pre-existing spare drive could essentially mean another stage of automatic redundancy, even if the RAID5 itself would only allow a one-drive failure.
Of course it is always necessary to have proper drive/failure monitoring and signaling so that a failed drive can be exchanged as soon as possible, no matter how much redundancy.
@Robert: May be wrong for your part of the world, but it seems that Dolby and Doremi are the servers that most screens use. If you are single screen with no chain/company/VPF implications, I would go with one of these two.
I started this thread not about servers in general, but about the new possibility of having DSS220/Doremi ShowVault + IMB even in installations where 4k is not planned (4k DLP so far was the only hard condition for IMB solutions).
When you are planning for early 2012, both Doremi ShowVault and DSS220 might be an option for you then. To me it seems IMB is more sustainable. I just don't know when it will be considered mature.
Of course, a traditional server with integrated media block is no dead-end. You can always upgrade to a series-II IMB later, and probably a Doremi 2k4 and DSS200 can be upgraded with the necessary IMB interface and software as well. It just costs more and it will need some retrofitting on the installation side.
- Carsten
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