SSD will change everything
So the imminent arrival of SSD in enterprise storage has got the old grey matter heating up somewhat. Below are a couple of things that I’ve come across in the last week that will be affected by the arrival of Flash based SSD in enterprise storage.
This list will no doubt grow……
As anybody who has ever needed to quickly cut some new LDEVs from existing internal RAID groups on Hitachi storage will already know – it takes an age!
• The process runs as a background task.
• All tracks are written with the new layout. (has anyone ever tried to recover data from an LDEV that was moved to space and then re-cut!!! Don’t waste your time)
So I was thinking, how will cutting LDEVs be affected by Solid State Disk?
Yes unfortunately I do know that Hitachi storage has no support for SSD, but Im hoping that will change sooner rather than later.
So…… considering the use of ‘wear levelling’ algorithms in SSD - one cannot be certain that when overwriting a
track cell they are actually overwriting the original cell, or if the drives internal algorithms have decided to target your write operation to a remapped cell - there seems no point writing to every cell when cutting your new LDEV if you cant be sure your future writes will actually be directed to the cells your are now formatting.
And then there’s the fact that unnecessary overwriting of storage cells is only going to reduce the life of your drive - and if the vendors will be replacing them under warranty then you can guarantee they wont be writing over cells unless its absolutely necessary.
So with these two points in mind, I see the arrival of SSD improving LDEV cutting times, bringing them in line with cutting LDEVs on external storage.
OK so its not exactly the main reason for implementing SSD, but will certainly make many a storage admins life easier.
On a similar point, last week a colleague asked me to show him how to use the Data Shredding program on a USP. After showing him I wondered how this too might be affected by SSD.
Basically, the Hitachi Data Shredding (HDS ) program allows you to overwrite every track of an LDEV several times (up to 8 last time I used it) with various patterns of data. The point being to guarantee that none of your customers data remains on the physical disk when its disposed of…..
Again, how would this be affected by the arrival of SSD, considering the fact that writing to every single track of an LDEV would –
1. Have an effect on the life of the media (especially if you choose to overwrite 8 times)
2. Not guarantee to overwrite the original data (due to wear levelling/remapping writes)
Granted I have only had the need to use the Data Shredding program twice in my life. The first time I used it, is took so long it took was ridiculous (if you thought cutting an LDEV took a long time, then you have never used the data shredder). So ridiculous that the second time it was decided not to use it because of time limitations.
Then there’s the occasional need for smaller faster drives (apologies to anyone who regularly reads this blog and is sick of me moaning about this). I have shook my head many a time over the one track (no pun intended) mind of the hard disk industry. Bigger bigger bigger!
Every once in a while I come across a situation where dedicated 73GB 15K disks would be ideal. But it’s just so hard to get them these days. While moaning about this in the past, rarely did I imagine I would one day be blessed with not only smaller capacity drives, but solid state!! Not only are the current generation of flash based single cell solid state disks smaller in capacity than traditional spinning disks, they are also faster. Bring it on!
You have to wonder what the disk manufacturers and array vendors think of the possible explosion of SSD into the mainstream? Are they eyeing up the current crop of SSD companies with the view to buying some of them up? Surely Seagate will have half an eye on this!
May be now is a good time to buy shares in some of these SSD players!?
So I guess now that Ive said all of that, only one small thing remains - Hitachi to announce support for SSD in the USP-V. Otherwise I will just have watch the rest with wanton eyes.